1 ===========================================
2 Clang |release| |ReleaseNotesTitle|
3 ===========================================
9 Written by the `LLVM Team <https://llvm.org/>`_
14 These are in-progress notes for the upcoming Clang |version| release.
15 Release notes for previous releases can be found on
16 `the Releases Page <https://llvm.org/releases/>`_.
21 This document contains the release notes for the Clang C/C++/Objective-C
22 frontend, part of the LLVM Compiler Infrastructure, release |release|. Here we
23 describe the status of Clang in some detail, including major
24 improvements from the previous release and new feature work. For the
25 general LLVM release notes, see `the LLVM
26 documentation <https://llvm.org/docs/ReleaseNotes.html>`_. For the libc++ release notes,
27 see `this page <https://libcxx.llvm.org/ReleaseNotes.html>`_. All LLVM releases
28 may be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.
30 For more information about Clang or LLVM, including information about the
31 latest release, please see the `Clang Web Site <https://clang.llvm.org>`_ or the
32 `LLVM Web Site <https://llvm.org>`_.
34 Potentially Breaking Changes
35 ============================
36 These changes are ones which we think may surprise users when upgrading to
37 Clang |release| because of the opportunity they pose for disruption to existing
41 C/C++ Language Potentially Breaking Changes
42 -------------------------------------------
43 - Indirect edges of asm goto statements under certain circumstances may now be
44 split. In previous releases of clang, that means for the following code the
45 two inputs may have compared equal in the inline assembly. This is no longer
46 guaranteed (and necessary to support outputs along indirect edges, which is
47 now supported as of this release). This change is more consistent with the
52 foo: asm goto ("# %0 %1"::"i"(&&foo)::foo);
54 - ``__builtin_object_size`` and ``__builtin_dynamic_object_size`` now add the
55 ``sizeof`` the elements specified in designated initializers of flexible
56 array members for structs that contain them. This change is more consistent
57 with the behavior of GCC.
59 C++ Specific Potentially Breaking Changes
60 -----------------------------------------
61 - Clang won't search for coroutine_traits in std::experimental namespace any more.
62 Clang will only search for std::coroutine_traits for coroutines then.
63 - Clang no longer allows dereferencing of a ``void *`` as an extension. Clang 16
64 converted this to a default-error as ``-Wvoid-ptr-dereference``, as well as a
65 SFINAE error. This flag is still valid however, as it disables the equivalent
68 ABI Changes in This Version
69 ---------------------------
70 - A bug in evaluating the ineligibility of some special member functions has been fixed. This can
71 make some classes trivially copyable that were not trivially copyable before. (`#62555 <https://github.com/llvm/llvm-project/issues/62555>`_)
73 What's New in Clang |release|?
74 ==============================
75 Some of the major new features and improvements to Clang are listed
76 here. Generic improvements to Clang as a whole or to its underlying
77 infrastructure are described first, followed by language-specific
78 sections with improvements to Clang's support for those languages.
82 - Improved ``-O0`` code generation for calls to ``std::forward_like``. Similarly to
83 ``std::move, std::forward`` et al. it is now treated as a compiler builtin and implemented
84 directly rather than instantiating the definition from the standard library.
85 - Implemented `CWG2518 <https://wg21.link/CWG2518>`_ which allows ``static_assert(false)``
86 to not be ill-formed when its condition is evaluated in the context of a template definition.
87 - Declaring namespace std to be an inline namespace is now prohibited, `[namespace.std]p7`.
88 - Improved code generation for ``dynamic_cast`` to a ``final`` type. Instead of
89 dispatching to the runtime library to compare the RTTI data, Clang now
90 generates a direct comparison of the vtable pointer in cases where the ABI
91 requires the vtable for a class to be unique. This optimization can be
92 disabled with ``-fno-assume-unique-vtables``. This optimization is not yet
93 implemented for the MS C++ ABI.
97 - Implemented the rule introduced by `CA104 <https://wg21.link/P2103R0>`_ for comparison of
98 constraint-expressions. Improved support for out-of-line definitions of constrained templates.
100 `#49620 <https://github.com/llvm/llvm-project/issues/49620>`_,
101 `#60231 <https://github.com/llvm/llvm-project/issues/60231>`_,
102 `#61414 <https://github.com/llvm/llvm-project/issues/61414>`_,
103 `#61809 <https://github.com/llvm/llvm-project/issues/61809>`_.
104 - Lambda templates with a requires clause directly after the template parameters now parse
105 correctly if the requires clause consists of a variable with a dependent type.
106 (`#61278 <https://github.com/llvm/llvm-project/issues/61278>`_)
107 - Announced C++20 Coroutines is fully supported on all targets except Windows, which
108 still has some stability and ABI issues.
109 - Downgraded use of a reserved identifier in a module export declaration from
110 an error to a warning under the ``-Wreserved-module-identifier`` warning
111 group. This warning is enabled by default. This addresses `#61446
112 <https://github.com/llvm/llvm-project/issues/61446>`_ and allows easier
113 building of standard modules. This diagnostic may be strengthened into an
114 error again in the future once there is a less fragile way to mark a module
115 as being part of the implementation rather than a user module.
116 - Clang now implements `[temp.deduct]p9`. Substitution failures inside lambdas from
117 unevaluated contexts will be surfaced as errors. They were previously handled as
119 - Clang now supports `requires cplusplus20` for module maps.
120 - Implemented missing parts of `P2002R1: Consistent comparison operators <https://wg21.link/P2002R1>`_
121 - Clang now defines `__cpp_consteval` macro.
122 - Implemented `P1816R0: <https://wg21.link/p1816r0>`_ and `P2082R1: <https://wg21.link/p2082r1>`_,
123 which allows CTAD for aggregates.
125 C++23 Feature Support
126 ^^^^^^^^^^^^^^^^^^^^^
128 - Implemented `P2036R3: Change scope of lambda trailing-return-type <https://wg21.link/P2036R3>`_
129 and `P2579R0 Mitigation strategies for P2036 <https://wg21.link/P2579R0>`_.
130 These proposals modify how variables captured in lambdas can appear in trailing return type
131 expressions and how their types are deduced therein, in all C++ language versions.
132 - Implemented partial support for `P2448R2: Relaxing some constexpr restrictions <https://wg21.link/p2448r2>`_
133 Explicitly defaulted functions no longer have to be constexpr-compatible but merely constexpr suitable.
134 We do not support outside of defaulted special memeber functions the change that constexpr functions no
135 longer have to be constexpr compatible but rather support a less restricted requirements for constexpr
136 functions. Which include allowing non-literal types as return values and parameters, allow calling of
137 non-constexpr functions and constructors.
138 - Clang now supports `requires cplusplus23` for module maps.
139 - Implemented `P2564R3: consteval needs to propagate up <https://wg21.link/P2564R3>`_.
141 C++2c Feature Support
142 ^^^^^^^^^^^^^^^^^^^^^
143 - Compiler flags ``-std=c++2c`` and ``-std=gnu++2c`` have been added for experimental C++2c implementation work.
144 - Implemented `P2738R1: constexpr cast from void* <https://wg21.link/P2738R1>`_.
145 - Partially implemented `P2361R6: Unevaluated strings <https://wg21.link/P2361R6>`_.
146 The changes to attributes declarations are not part of this release.
147 - Implemented `P2741R3: user-generated static_assert messages <https://wg21.link/P2741R3>`_.
149 Resolutions to C++ Defect Reports
150 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
151 - Implemented `DR2397 <https://wg21.link/CWG2397>`_ which allows ``auto`` specifier for pointers
152 and reference to arrays.
153 - Implemented `CWG2521 <https://wg21.link/CWG2521>`_ which reserves using ``__`` in user-defined
154 literal suffixes and deprecates literal operator function declarations using an identifier.
155 Taught ``-Wuser-defined-literals`` for the former, on by default, and added
156 ``-Wdeprecated-literal-operator`` for the latter, off by default for now.
160 // What follows is warned by -Wuser-defined-literals
161 // albeit "ill-formed, no diagnostic required".
162 // Its behavior is undefined, [reserved.names.general]p2.
163 string operator ""__i18n(const char*, std::size_t);
165 // Assume this declaration is not in the global namespace.
166 // -Wdeprecated-literal-operator diagnoses the extra space.
167 string operator "" _i18n(const char*, std::size_t);
172 - Support for outputs from asm goto statements along indirect edges has been
173 added. (`#53562 <https://github.com/llvm/llvm-project/issues/53562>`_)
174 - Fixed a bug that prevented initialization of an ``_Atomic``-qualified pointer
175 from a null pointer constant.
176 - Fixed a bug that prevented casting to an ``_Atomic``-qualified type.
177 (`#39596 <https://github.com/llvm/llvm-project/issues/39596>`_)
178 - Added an extension to ``_Generic`` which allows the first operand to be a
179 type rather than an expression. The type does not undergo any conversions,
180 which makes this feature suitable for matching qualified types, incomplete
181 types, and function or array types.
186 _Generic(i, int : 0, const int : 1); // Warns about unreachable code, the
187 // result is 0, not 1.
188 _Generic(typeof(i), int : 0, const int : 1); // Result is 1, not 0.
189 - ``structs``, ``unions``, and ``arrays`` that are const may now be used as
190 constant expressions. This change is more consistent with the behavior of
195 - Implemented the ``unreachable`` macro in freestanding ``<stddef.h>`` for
196 `WG14 N2826 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2826.pdf>`_
198 - Removed the ``ATOMIC_VAR_INIT`` macro in C2x and later standards modes, which
199 implements `WG14 N2886 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2886.htm>`_
201 - Implemented `WG14 N2934 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2934.pdf>`_
202 which introduces the ``bool``, ``static_assert``, ``alignas``, ``alignof``,
203 and ``thread_local`` keywords in C2x.
205 - Implemented `WG14 N2900 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm>`_
206 and `WG14 N3011 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3011.htm>`_
207 which allows for empty braced initialization in C.
211 struct S { int x, y } s = {}; // Initializes s.x and s.y to 0
213 As part of this change, the ``-Wgnu-empty-initializer`` warning group was
214 removed, as this is no longer a GNU extension but a C2x extension. You can
215 use ``-Wno-c2x-extensions`` to silence the extension warning instead.
217 - Updated the implementation of
218 `WG14 N3042 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3042.htm>`_
219 based on decisions reached during the WG14 CD Ballot Resolution meetings held
220 in Jan and Feb 2023. This should complete the implementation of ``nullptr``
221 and ``nullptr_t`` in C. The specific changes are:
225 void func(nullptr_t);
226 func(0); // Previously required to be rejected, is now accepted.
227 func((void *)0); // Previously required to be rejected, is now accepted.
230 val = 0; // Previously required to be rejected, is now accepted.
231 val = (void *)0; // Previously required to be rejected, is now accepted.
233 bool b = nullptr; // Was incorrectly rejected by Clang, is now accepted.
235 - Implemented `WG14 N3124 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3124.pdf>_`,
236 which allows any universal character name to appear in character and string literals.
239 Non-comprehensive list of changes in this release
240 -------------------------------------------------
241 - Clang now saves the address of ABI-indirect function parameters on the stack,
242 improving the debug information available in programs compiled without
244 - Clang now supports ``__builtin_nondeterministic_value`` that returns a
245 nondeterministic value of the same type as the provided argument.
246 - Clang now supports ``__builtin_FILE_NAME()`` which returns the same
247 information as the ``__FILE_NAME__`` macro (the presumed file name
248 from the invocation point, with no path components included).
249 - Clang now supports ``__builtin_assume_separate_storage`` that indicates that
250 its arguments point to objects in separate storage allocations.
251 - Clang now supports expressions in ``#pragma clang __debug dump``.
252 - Clang now supports declaration of multi-dimensional arrays with
253 ``__declspec(property)``.
254 - A new builtin type trait ``__is_trivially_equality_comparable`` has been added,
255 which checks whether comparing two instances of a type is equivalent to
256 ``memcmp(&lhs, &rhs, sizeof(T)) == 0``.
257 - Clang now ignores null directives outside of the include guard when deciding
258 whether a file can be enabled for the multiple-include optimization.
259 - Clang now support ``__builtin_FUNCSIG()`` which returns the same information
260 as the ``__FUNCSIG__`` macro (available only with ``-fms-extensions`` flag).
261 This fixes (`#58951 <https://github.com/llvm/llvm-project/issues/58951>`_).
262 - Clang now supports the `NO_COLOR <https://no-color.org/>`_ environment
263 variable as a way to disable color diagnostics.
264 - Clang now supports ``__builtin_isfpclass``, which checks if the specified
265 floating-point value falls into any of the specified data classes.
266 - Added ``__builtin_elementwise_round`` for builtin for floating
267 point types. This allows access to ``llvm.round`` for
268 arbitrary floating-point and vector of floating-point types.
269 - Added ``__builtin_elementwise_rint`` for floating point types. This
270 allows access to ``llvm.rint`` for arbitrary floating-point and
271 vector of floating-point types.
272 - Added ``__builtin_elementwise_nearbyint`` for floating point
273 types. This allows access to ``llvm.nearbyint`` for arbitrary
274 floating-point and vector of floating-point types.
275 - Clang AST matcher now matches concept declarations with `conceptDecl`.
276 - Clang now supports more GCC stdio builtins: ``__builtin_vprintf``, ``__builtin_vfprintf``,
277 ``__builtin_fscanf``, ``__builtin_scanf``, ``__builtin_sscanf``, ``__builtin_vfscanf``,
278 ``__builtin_vscanf``, ``__builtin_vsscanf``.
283 - The flag ``-std=c++23`` has been added. This behaves the same as the existing
285 - ``-dumpdir`` has been implemented to specify auxiliary and dump output
286 filenames for features like ``-gsplit-dwarf``.
287 - ``-fcaret-diagnostics-max-lines=`` has been added as a driver options, which
288 lets users control the maximum number of source lines printed for a
290 - ``-fkeep-persistent-storage-variables`` has been implemented to keep all
291 variables that have a persistent storage duration—including global, static
292 and thread-local variables—to guarantee that they can be directly addressed.
293 Since this inhibits the merging of the affected variables, the number of
294 individual relocations in the program will generally increase.
295 - ``-f[no-]assume-unique-vtables`` controls whether Clang assumes that each
296 class has a unique vtable address, when that is required by the ABI.
297 - ``-print-multi-flags-experimental`` prints the flags used for multilib
298 selection. See `the multilib docs <https://clang.llvm.org/docs/Multilib.html>`_
300 - ``-maix32`` and ``-maix64`` are new GCC compatibility flags that select the
301 bitmode to target on AIX.
302 - ``-p`` is a new GCC compatibility flag for AIX and Linux which works
303 similarly to ``-pg`` by writing profile information, but targets the ``prof``
304 tool as opposed to the ``gprof`` tool.
306 Deprecated Compiler Flags
307 -------------------------
309 - ``-fdouble-square-bracket-attributes`` has been deprecated. It is ignored now
310 and will be removed in Clang 18.
312 Modified Compiler Flags
313 -----------------------
315 - ``clang -g -gsplit-dwarf a.c -o obj/x`` (compile and link) now generates the
316 ``.dwo`` file at ``obj/x-a.dwo``, instead of a file in the temporary
317 directory (``/tmp`` on \*NIX systems, if none of the environment variables
318 TMPDIR, TMP, and TEMP are specified).
320 Removed Compiler Flags
321 -------------------------
322 - The deprecated flag `-fmodules-ts` is removed. Please use ``-std=c++20``
323 or higher to use standard C++ modules instead.
324 - The deprecated flag `-fcoroutines-ts` is removed. Please use ``-std=c++20``
325 or higher to use standard C++ coroutines instead.
326 - The CodeGen flag `-lower-global-dtors-via-cxa-atexit` which affects how global
327 destructors are lowered for MachO is removed without replacement. The default
328 of `-lower-global-dtors-via-cxa-atexit=true` is now the only supported way.
329 - The cc1 flag ``-no-opaque-pointers`` has been removed.
331 Attribute Changes in Clang
332 --------------------------
333 - Introduced a new function attribute ``__attribute__((unsafe_buffer_usage))``
334 to be worn by functions containing buffer operations that could cause out of
335 bounds memory accesses. It emits warnings at call sites to such functions when
336 the flag ``-Wunsafe-buffer-usage`` is enabled.
337 - ``__declspec`` attributes can now be used together with the using keyword. Before
338 the attributes on ``__declspec`` was ignored, while now it will be forwarded to the
339 point where the alias is used. Note, some incorrect uses of ``__declspec`` on a
340 ``using`` declaration were being silently ignored and will now be appropriately
341 diagnosed as ignoring the attribute.
342 - Introduced a new ``USR`` (unified symbol resolution) clause inside of the
343 existing ``__attribute__((external_source_symbol))`` attribute. Clang's indexer
344 uses the optional USR value when indexing Clang's AST. This value is expected
345 to be generated by an external compiler when generating C++ bindings during
346 the compilation of the foreign language sources (e.g. Swift).
347 - The ``__has_attribute``, ``__has_c_attribute`` and ``__has_cpp_attribute``
348 preprocessor operators now return 1 also for attributes defined by plugins.
349 - Improve the AST fidelity of ``alignas`` and ``_Alignas`` attribute. Before, we
350 model ``alignas(type-id)`` as though the user wrote ``alignas(alignof(type-id))``,
351 now we directly use ``alignas(type-id)``.
353 Improvements to Clang's diagnostics
354 -----------------------------------
355 - We now generate a diagnostic for signed integer overflow due to unary minus
356 in a non-constant expression context.
357 (`#31643 <https://github.com/llvm/llvm-project/issues/31643>`_)
358 - Clang now warns by default for C++20 and later about deprecated capture of
359 ``this`` with a capture default of ``=``. This warning can be disabled with
360 ``-Wno-deprecated-this-capture``.
361 - Clang had failed to emit some ``-Wundefined-internal`` for members of a local
362 class if that class was first introduced with a forward declaration.
363 - Diagnostic notes and fix-its are now generated for ``ifunc``/``alias`` attributes
364 which point to functions whose names are mangled.
365 - Diagnostics relating to macros on the command line of a preprocessed assembly
366 file or precompiled header are now reported as coming from the file
367 ``<command line>`` instead of ``<built-in>``.
368 - Clang constexpr evaluator now provides a more concise diagnostic when calling
369 function pointer that is known to be null.
370 - Clang now avoids duplicate warnings on unreachable ``[[fallthrough]];`` statements
371 previously issued from ``-Wunreachable-code`` and ``-Wunreachable-code-fallthrough``
372 by prioritizing ``-Wunreachable-code-fallthrough``.
373 - Clang now correctly diagnoses statement attributes ``[[clang::always_inline]]`` and
374 ``[[clang::noinline]]`` when used on a statement with dependent call expressions.
375 - Clang now checks for completeness of the second and third arguments in the
376 conditional operator.
377 (`#59718 <https://github.com/llvm/llvm-project/issues/59718>`_)
378 - There were some cases in which the diagnostic for the unavailable attribute
379 might not be issued, this fixes those cases.
380 (`61815 <https://github.com/llvm/llvm-project/issues/61815>`_)
381 - Clang now avoids unnecessary diagnostic warnings for obvious expressions in
382 the case of binary operators with logical OR operations.
383 (`#57906 <https://github.com/llvm/llvm-project/issues/57906>`_)
384 - Clang's "static assertion failed" diagnostic now points to the static assertion
385 expression instead of pointing to the ``static_assert`` token.
386 (`#61951 <https://github.com/llvm/llvm-project/issues/61951>`_)
387 - ``-Wformat`` now recognizes ``%lb`` for the ``printf``/``scanf`` family of
389 (`#62247: <https://github.com/llvm/llvm-project/issues/62247>`_).
390 - Clang now diagnoses shadowing of lambda's template parameter by a capture.
391 (`#61105: <https://github.com/llvm/llvm-project/issues/61105>`_).
392 - Address a false positive in ``-Wpacked`` when applied to a non-pod type using
394 (`#62353: <https://github.com/llvm/llvm-project/issues/62353>`_,
395 fallout from the non-POD packing ABI fix in LLVM 15).
396 - Clang constexpr evaluator now prints subobject's name instead of its type in notes
397 when a constexpr variable has uninitialized subobjects after its constructor call.
398 (`#58601 <https://github.com/llvm/llvm-project/issues/58601>`_)
399 - Clang's `-Wshadow` warning now warns about shadowings by static local variables
400 (`#62850: <https://github.com/llvm/llvm-project/issues/62850>`_).
401 - Clang now warns when any predefined macro is undefined or redefined, instead
402 of only some of them.
403 - Clang now correctly diagnoses when the argument to ``alignas`` or ``_Alignas``
404 is an incomplete type.
405 (`#55175: <https://github.com/llvm/llvm-project/issues/55175>`_, and fixes an
406 incorrect mention of ``alignof`` in a diagnostic about ``alignas``).
407 - Clang will now show a margin with line numbers to the left of each line
408 of code it prints for diagnostics. This can be disabled using
409 ``-fno-diagnostics-show-line-numbers``. At the same time, the maximum
410 number of code lines it prints has been increased from 1 to 16. This
411 can be controlled using ``-fcaret-diagnostics-max-lines=``.
412 - Clang no longer emits ``-Wunused-variable`` warnings for variables declared
413 with ``__attribute__((cleanup(...)))`` to match GCC's behavior.
414 - Clang now issues expected warnings for situations of comparing with NULL pointers.
415 (`#42992: <https://github.com/llvm/llvm-project/issues/42992>`_)
416 - Clang now diagnoses unused const-qualified variable template as
417 "unused variable template" rather than "unused variable".
418 - When diagnosing a constant expression where an enum without a fixed underlying
419 type is set to a value outside the range of the enum's values, clang will now
420 print the name of the enum in question.
421 - Clang no longer diagnoses a read of an empty structure as use of an
422 uninitialized variable.
423 (`#26842: <https://github.com/llvm/llvm-project/issues/26842>`_)
424 - The Fix-It emitted for unused labels used to expand to the next line, which caused
425 visual oddities now that Clang shows more than one line of code snippet. This has
426 been fixed and the Fix-It now only spans to the end of the ``:``.
427 - Clang now underlines the parameter list of function declaration when emitting
428 a note about the mismatch in the number of arguments.
429 - Clang now diagnoses unexpected tokens after a
430 ``#pragma clang|GCC diagnostic push|pop`` directive.
431 (`#13920: <https://github.com/llvm/llvm-project/issues/13920>`_)
432 - Clang now does not try to analyze cast validity on variables with dependent alignment (`#63007: <https://github.com/llvm/llvm-project/issues/63007>`_).
433 - Clang constexpr evaluator now displays member function calls more precisely
434 by making use of the syntactical structure of function calls. This avoids display
435 of syntactically invalid codes in diagnostics.
436 (`#57081: <https://github.com/llvm/llvm-project/issues/57081>`_)
437 - Clang no longer emits inappropriate notes about the loss of ``__unaligned`` qualifier
438 on overload resolution, when the actual reason for the failure is loss of other qualifiers.
439 - The note emitted when an ``operator==`` was defaulted as deleted used to refer to
440 the lack of a data member's "three-way comparison operator". It now refers correctly
441 to the data member's ``operator==``.
442 (`#63960: <https://github.com/llvm/llvm-project/issues/63960>`_)
443 - Clang's notes about unconvertible types in overload resolution failure now covers
444 the source range of parameter declaration of the candidate function declaration.
450 void func(int aa, int bb);
451 void test() { func(1, "two"); }
457 source:2:15: error: no matching function for call to 'func'
458 void test() { func(1, "two"); }
460 source:1:6: note: candidate function not viable: no known conversion from 'const char[4]' to 'int' for 2nd argument
461 void func(int aa, int bb);
468 source:2:15: error: no matching function for call to 'func'
469 void test() { func(1, "two"); }
471 source:1:6: note: candidate function not viable: no known conversion from 'const char[4]' to 'int' for 2nd argument
472 void func(int aa, int bb);
475 - ``-Wformat`` cast fix-its will now suggest ``static_cast`` instead of C-style casts
477 - ``-Wformat`` will no longer suggest a no-op fix-it for fixing scoped enum format
478 warnings. Instead, it will suggest casting the enum object based on its
481 Bug Fixes in This Version
482 -------------------------
483 - Fixed an issue where a class template specialization whose declaration is
484 instantiated in one module and whose definition is instantiated in another
485 module may end up with members associated with the wrong declaration of the
486 class, which can result in miscompiles in some cases.
487 - Added a new diagnostic warning group
488 ``-Wdeprecated-redundant-constexpr-static-def``, under the existing
489 ``-Wdeprecated`` group. This controls warnings about out-of-line definitions
490 of 'static constexpr' data members that are unnecessary from C++17 onwards.
491 - Fix segfault while running clang-rename on a non existing file.
492 (`#36471 <https://github.com/llvm/llvm-project/issues/36471>`_)
493 - Fix crash when diagnosing incorrect usage of ``_Nullable`` involving alias
495 (`#60344 <https://github.com/llvm/llvm-project/issues/60344>`_)
496 - Fix confusing warning message when ``/clang:-x`` is passed in ``clang-cl``
497 driver mode and emit an error which suggests using ``/TC`` or ``/TP``
498 ``clang-cl`` options instead.
499 (`#59307 <https://github.com/llvm/llvm-project/issues/59307>`_)
500 - Fix assert that fails when the expression causing the this pointer to be
501 captured by a block is part of a constexpr if statement's branch and
502 instantiation of the enclosing method causes the branch to be discarded.
503 - Fix __VA_OPT__ implementation so that it treats the concatenation of a
504 non-placemaker token and placemaker token as a non-placemaker token.
505 (`#60268 <https://github.com/llvm/llvm-project/issues/60268>`_)
506 - Fix crash when taking the address of a consteval lambda call operator.
507 (`#57682 <https://github.com/llvm/llvm-project/issues/57682>`_)
508 - Clang now support export declarations in the language linkage.
509 (`#60405 <https://github.com/llvm/llvm-project/issues/60405>`_)
510 - Fix aggregate initialization inside lambda constexpr.
511 (`#60936 <https://github.com/llvm/llvm-project/issues/60936>`_)
512 - No longer issue a false positive diagnostic about a catch handler that cannot
513 be reached despite being reachable. This fixes
514 `#61177 <https://github.com/llvm/llvm-project/issues/61177>`_ in anticipation
515 of `CWG2699 <https://wg21.link/CWG2699>_` being accepted by WG21.
516 - Fix crash when parsing fold expression containing a delayed typo correction.
517 (`#61326 <https://github.com/llvm/llvm-project/issues/61326>`_)
518 - Fix crash when dealing with some member accesses outside of class or member
520 (`#37792 <https://github.com/llvm/llvm-project/issues/37792>`_) and
521 (`#48405 <https://github.com/llvm/llvm-project/issues/48405>`_)
522 - Fix crash when using ``[[clang::always_inline]]`` or ``[[clang::noinline]]``
523 statement attributes on a call to a template function in the body of a
525 - Fix coroutines issue where ``get_return_object()`` result was always eagerly
526 converted to the return type. Eager initialization (allowing RVO) is now only
527 performed when these types match, otherwise deferred initialization is used,
528 enabling short-circuiting coroutines use cases. This fixes
529 (`#56532 <https://github.com/llvm/llvm-project/issues/56532>`_) in
530 anticipation of `CWG2563 <https://cplusplus.github.io/CWG/issues/2563.html>_`.
531 - Fix highlighting issue with ``_Complex`` and initialization list with more than
532 2 items. (`#61518 <https://github.com/llvm/llvm-project/issues/61518>`_)
533 - Fix ``getSourceRange`` on ``VarTemplateSpecializationDecl`` and
534 ``VarTemplatePartialSpecializationDecl``, which represents variable with
535 the initializer, so it behaves consistently with other ``VarDecls`` and ends
536 on the last token of initializer, instead of right angle bracket of
537 the template argument list.
538 - Fix false-positive diagnostic issued for consteval initializers of temporary
540 (`#60286 <https://github.com/llvm/llvm-project/issues/60286>`_)
541 - Correct restriction of trailing requirements clauses on a templated function.
542 Previously we only rejected non-'templated' things, but the restrictions ALSO need
543 to limit non-defined/non-member functions as well. Additionally, we now diagnose
544 requires on lambdas when not allowed, which we previously missed.
545 (`#61748 <https://github.com/llvm/llvm-project/issues/61748>`_)
546 - Fix confusing diagnostic for incorrect use of qualified concepts names.
547 - Fix handling of comments in function like macros so they are ignored in -CC
549 (`#60887 <https://github.com/llvm/llvm-project/issues/60887>`_)
550 - Fix incorrect merging of lambdas across modules.
551 (`#60985 <https://github.com/llvm/llvm-project/issues/60985>`_)
552 - Fix crash when handling nested immediate invocations in initializers of global
554 (`#58207 <https://github.com/llvm/llvm-project/issues/58207>`_)
555 - Fix crash when generating code coverage information for `PseudoObjectExpr` in
557 (`#45481 <https://github.com/llvm/llvm-project/issues/45481>`_)
558 - Fix the assertion hit when a template consteval function appears in a nested
559 consteval/constexpr call chain.
560 (`#61142 <https://github.com/llvm/llvm-project/issues/61142>`_)
561 - Clang now better diagnose placeholder types constrained with a concept that is
563 - Fix crash when a doc comment contains a line splicing.
564 (`#62054 <https://github.com/llvm/llvm-project/issues/62054>`_)
565 - Work around with a clang coverage crash which happens when visiting
566 expressions/statements with invalid source locations in non-assert builds.
567 Assert builds may still see assertions triggered from this.
568 - Fix a failed assertion due to an invalid source location when trying to form
569 a coverage report for an unresolved constructor expression.
570 (`#62105 <https://github.com/llvm/llvm-project/issues/62105>`_)
571 - Fix defaulted equality operator so that it does not attempt to compare unnamed
572 bit-fields. This fixes:
573 (`#61355 <https://github.com/llvm/llvm-project/issues/61335>`_) and
574 (`#61417 <https://github.com/llvm/llvm-project/issues/61417>`_)
575 - Fix crash after suggesting typo correction to constexpr if condition.
576 (`#61885 <https://github.com/llvm/llvm-project/issues/61885>`_)
577 - Clang constexpr evaluator now treats comparison of [[gnu::weak]]-attributed
578 member pointer as an invalid expression.
579 - Fix crash when member function contains invalid default argument.
580 (`#62122 <https://github.com/llvm/llvm-project/issues/62122>`_)
581 - Fix crash when handling undefined template partial specialization
582 (`#61356 <https://github.com/llvm/llvm-project/issues/61356>`_)
583 - Fix premature substitution into the constraints of an inherited constructor.
584 - Fix crash when attempting to perform parenthesized initialization of an
585 aggregate with a base class with only non-public constructors.
586 (`#62296 <https://github.com/llvm/llvm-project/issues/62296>`_)
587 - Fix crash when handling initialization candidates for invalid deduction guide.
588 (`#62408 <https://github.com/llvm/llvm-project/issues/62408>`_)
589 - Fix crash when redefining a variable with an invalid type again with an
590 invalid type. (`#62447 <https://github.com/llvm/llvm-project/issues/62447>`_)
591 - Fix a stack overflow issue when evaluating ``consteval`` default arguments.
592 (`#60082 <https://github.com/llvm/llvm-project/issues/60082>`_)
593 - Fix the assertion hit when generating code for global variable initializer of
595 (`#62207 <https://github.com/llvm/llvm-project/issues/62207>`_)
596 - Fix lambdas and other anonymous function names not respecting ``-fdebug-prefix-map``
597 (`#62192 <https://github.com/llvm/llvm-project/issues/62192>`_)
598 - Fix crash when attempting to pass a non-pointer type as first argument of
599 ``__builtin_assume_aligned``.
600 (`#62305 <https://github.com/llvm/llvm-project/issues/62305>`_)
601 - A default argument for a non-type template parameter is evaluated and checked
602 at the point where it is required. This fixes:
603 (`#62224 <https://github.com/llvm/llvm-project/issues/62224>`_) and
604 (`#62596 <https://github.com/llvm/llvm-project/issues/62596>`_)
605 - Fix an assertion when instantiating the body of a Class Template Specialization
606 when it had been instantiated from a partial template specialization with different
607 template arguments on the containing class. This fixes:
608 (`#60778 <https://github.com/llvm/llvm-project/issues/60778>`_).
609 - Fix a crash when an enum constant has a dependent-type recovery expression for
611 (`#62446 <https://github.com/llvm/llvm-project/issues/62446>`_).
612 - Propagate the value-dependent bit for VAArgExpr. Fixes a crash where a
613 __builtin_va_arg call has invalid arguments.
614 (`#62711 <https://github.com/llvm/llvm-project/issues/62711>`_).
615 - Fix crash on attempt to initialize union with flexible array member.
616 (`#61746 <https://github.com/llvm/llvm-project/issues/61746>`_).
617 - Clang `TextNodeDumper` enabled through `-ast-dump` flag no longer evaluates the
618 initializer of constexpr `VarDecl` if the declaration has a dependent type.
619 - Match GCC's behavior for ``__builtin_object_size`` and
620 ``__builtin_dynamic_object_size`` on structs containing flexible array
622 (`#62789 <https://github.com/llvm/llvm-project/issues/62789>`_).
623 - Fix a crash when instantiating a non-type template argument in a dependent scope.
624 (`#62533 <https://github.com/llvm/llvm-project/issues/62533>`_).
625 - Fix crash when diagnosing default comparison method.
626 (`#62791 <https://github.com/llvm/llvm-project/issues/62791>`_) and
627 (`#62102 <https://github.com/llvm/llvm-project/issues/62102>`_).
628 - Fix crash when passing a braced initializer list to a parentehsized aggregate
629 initialization expression.
630 (`#63008 <https://github.com/llvm/llvm-project/issues/63008>`_).
631 - Reject increment of bool value in unevaluated contexts after C++17.
632 (`#47517 <https://github.com/llvm/llvm-project/issues/47517>`_).
633 - Fix assertion and quality of diagnostic messages in a for loop
634 containing multiple declarations and a range specifier
635 (`#63010 <https://github.com/llvm/llvm-project/issues/63010>`_).
636 - Fix rejects-valid when consteval operator appears inside of a template.
637 (`#62886 <https://github.com/llvm/llvm-project/issues/62886>`_).
638 - Fix crash for code using ``_Atomic`` types in C++
639 (`See patch <https://reviews.llvm.org/D152303>`_).
640 - Fix crash when passing a value larger then 64 bits to the aligned attribute.
641 (`#50534 <https://github.com/llvm/llvm-project/issues/50534>`_).
642 - CallExpr built for C error-recovery now is always type-dependent. Fixes a
643 crash when we encounter a unresolved TypoExpr during diagnostic emission.
644 (`#50244 <https://github.com/llvm/llvm-project/issues/50244>`_).
645 - Apply ``-fmacro-prefix-map`` to anonymous tags in template arguments
646 (`#63219 <https://github.com/llvm/llvm-project/issues/63219>`_).
647 - Clang now properly diagnoses format string mismatches involving scoped
648 enumeration types. A scoped enumeration type is not promoted to an integer
649 type by the default argument promotions, and thus this is UB. Clang's
650 behavior now matches GCC's behavior in C++.
651 (`#38717 <https://github.com/llvm/llvm-project/issues/38717>`_).
652 - Fixed a failing assertion when implicitly defining a function within a GNU
653 statement expression that appears outside of a function block scope. The
654 assertion was benign outside of asserts builds and would only fire in C.
655 (`#48579 <https://github.com/llvm/llvm-project/issues/48579>`_).
656 - Fixed a failing assertion when applying an attribute to an anonymous union.
657 The assertion was benign outside of asserts builds and would only fire in C++.
658 (`#48512 <https://github.com/llvm/llvm-project/issues/48512>`_).
659 - Fixed a failing assertion when parsing incomplete destructor.
660 (`#63503 <https://github.com/llvm/llvm-project/issues/63503>`_)
661 - Fix C++17 mode assert when parsing malformed code and the compiler is
662 attempting to see if it could be type template for class template argument
663 deduction. This fixes
664 (`Issue 57495 <https://github.com/llvm/llvm-project/issues/57495>`_)
665 - Fix missing destructor calls and therefore memory leaks in generated code
666 when an immediate invocation appears as a part of an expression that produces
668 (`#60709 <https://github.com/llvm/llvm-project/issues/60709>`_).
669 - Fixed a missed integer overflow warning with temporary values.
670 (`#63629 <https://github.com/llvm/llvm-project/issues/63629>`_)
671 - Fixed parsing of elaborated type specifier inside of a new expression.
672 (`#34341 <https://github.com/llvm/llvm-project/issues/34341>`_)
673 - Clang now correctly evaluates ``__has_extension (cxx_defaulted_functions)``
674 and ``__has_extension (cxx_default_function_template_args)`` to 1.
675 (`#61758 <https://github.com/llvm/llvm-project/issues/61758>`_)
676 - Stop evaluating a constant expression if the condition expression which in
677 switch statement contains errors.
678 (`#63453 <https://github.com/llvm/llvm-project/issues/63453>_`)
679 - Fixed false positive error diagnostic when pack expansion appears in template
680 parameters of a member expression.
681 (`#48731 <https://github.com/llvm/llvm-project/issues/48731>`_)
682 - Fix the contains-errors bit not being set for DeclRefExpr that refers to a
683 VarDecl with invalid initializer. This fixes:
684 (`#50236 <https://github.com/llvm/llvm-project/issues/50236>`_),
685 (`#50243 <https://github.com/llvm/llvm-project/issues/50243>`_),
686 (`#48636 <https://github.com/llvm/llvm-project/issues/48636>`_),
687 (`#50320 <https://github.com/llvm/llvm-project/issues/50320>`_).
688 - Fix an assertion when using ``\u0024`` (``$``) as an identifier, by disallowing
689 that construct (`#62133 <https://github.com/llvm/llvm-project/issues/38717>_`).
690 - Fix crash caused by PseudoObjectExprBitfields: NumSubExprs overflow.
691 (`#63169 <https://github.com/llvm/llvm-project/issues/63169>_`)
692 - Fix crash when casting an object to an array type.
693 (`#63758 <https://github.com/llvm/llvm-project/issues/63758>_`)
694 - Fixed false positive error diagnostic observed from mixing ``asm goto`` with
695 ``__attribute__((cleanup()))`` variables falsely warning that jumps to
696 non-targets would skip cleanup.
697 - Correcly diagnose jumps into statement expressions.
698 This ensures the behavior of Clang is consistent with GCC.
699 (`#63682 <https://github.com/llvm/llvm-project/issues/63682>`_)
700 - Invalidate BlockDecl with implicit return type, in case any of the return
701 value exprs is invalid. Propagating the error info up by replacing BlockExpr
702 with a RecoveryExpr. This fixes:
703 (`#63863 <https://github.com/llvm/llvm-project/issues/63863>_`)
704 - Invalidate BlockDecl with invalid ParmVarDecl. Remove redundant dump of
705 BlockDecl's ParmVarDecl
706 (`#64005 <https://github.com/llvm/llvm-project/issues/64005>_`)
707 - Fix crash on nested templated class with template function call.
708 (`#61159 <https://github.com/llvm/llvm-project/issues/61159>_`)
709 - Fix a hang on valid C code passing a function type as an argument to
710 ``typeof`` to form a function declaration.
711 (`#64713 <https://github.com/llvm/llvm-project/issues/64713>_`)
712 - Clang now correctly diagnoses ``function_needs_feature`` when always_inline
713 callee has incompatible target features with caller.
714 - Removed the linking of libraries when ``-r`` is passed to the driver on AIX.
715 - Fixed an Itanium ABI bug where we force exactly two-byte alignment on member
716 functions to reserve a bit in function pointers for identifying pointers to
717 virtual member functions even if the target required a greater function
718 alignment and/or did not have function pointers which point to function entry
719 points (i.e., uses function descriptor objects instead).
720 - Fixes a ``clang-17`` regression where ``LLVM_UNREACHABLE_OPTIMIZE=OFF``
721 cannot be used with ``Release`` mode builds. (`#68237 <https://github.com/llvm/llvm-project/issues/68237>`_).
722 - No longer use C++ ``thread_local`` semantics in C23 when using
723 ``thread_local`` instead of ``_Thread_local``.
724 Fixes (`#70068 <https://github.com/llvm/llvm-project/issues/70068>`_) and
725 (`#69167 <https://github.com/llvm/llvm-project/issues/69167>`_)
727 Bug Fixes to Compiler Builtins
728 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
730 Bug Fixes to Attribute Support
731 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
732 - Fixed a bug where attribute annotations on type specifiers (enums, classes,
733 structs, unions, and scoped enums) were not properly ignored, resulting in
734 misleading warning messages. Now, such attribute annotations are correctly
735 ignored. (`#61660 <https://github.com/llvm/llvm-project/issues/61660>`_)
736 - GNU attributes preceding C++ style attributes on templates were not properly
737 handled, resulting in compilation error. This has been corrected to match the
738 behavior exhibited by GCC, which permits mixed ordering of GNU and C++
741 Bug Fixes to C++ Support
742 ^^^^^^^^^^^^^^^^^^^^^^^^
744 - Fix crash on invalid code when looking up a destructor in a templated class
746 (`#59446 <https://github.com/llvm/llvm-project/issues/59446>`_)
747 - Fix crash when evaluating consteval constructor of derived class whose base
748 has more than one field.
749 (`#60166 <https://github.com/llvm/llvm-project/issues/60166>`_)
750 - Fix an issue about ``decltype`` in the members of class templates derived from
751 templates with related parameters.
752 (`#58674 <https://github.com/llvm/llvm-project/issues/58674>`_)
753 - Fix incorrect deletion of the default constructor of unions in some
754 cases. (`#48416 <https://github.com/llvm/llvm-project/issues/48416>`_)
755 - No longer issue a pre-C++23 compatibility warning in ``-pedantic`` mode
756 regarding overloaded `operator[]` with more than one parameter or for static
757 lambdas. (`#61582 <https://github.com/llvm/llvm-project/issues/61582>`_)
758 - Stop stripping CV qualifiers from the type of ``this`` when capturing it by value in
760 (`#50866 <https://github.com/llvm/llvm-project/issues/50866>`_)
761 - Fix ordering of function templates by constraints when they have template
762 template parameters with different nested constraints.
763 - Fix type equivalence comparison between auto types to take constraints into
765 - Fix bug in the computation of the ``__has_unique_object_representations``
766 builtin for types with unnamed bitfields.
767 (`#61336 <https://github.com/llvm/llvm-project/issues/61336>`_)
768 - Fix default member initializers sometimes being ignored when performing
769 parenthesized aggregate initialization of templated types.
770 (`#62266 <https://github.com/llvm/llvm-project/issues/62266>`_)
771 - Fix overly aggressive lifetime checks for parenthesized aggregate
773 (`#61567 <https://github.com/llvm/llvm-project/issues/61567>`_)
774 - Fix a crash when expanding a pack as the index of a subscript expression.
775 - Fix handling of constexpr dynamic memory allocations in template
776 arguments. (`#62462 <https://github.com/llvm/llvm-project/issues/62462>`_)
777 - Some predefined expressions are now treated as string literals in MSVC
779 (`#114 <https://github.com/llvm/llvm-project/issues/114>`_)
780 - Fix parsing of `auto(x)`, when it is surrounded by parentheses.
781 (`#62494 <https://github.com/llvm/llvm-project/issues/62494>`_)
782 - Fix handling of generic lambda used as template arguments.
783 (`#62611 <https://github.com/llvm/llvm-project/issues/62611>`_)
784 - Allow omitting ``typename`` in the parameter declaration of a friend
785 constructor declaration.
786 (`#63119 <https://github.com/llvm/llvm-project/issues/63119>`_)
787 - Fix access of a friend class declared in a local class. Clang previously
788 emitted an error when a friend of a local class tried to access it's
789 private data members.
790 - Allow abstract parameter and return types in functions that are
791 either deleted or not defined.
792 (`#63012 <https://github.com/llvm/llvm-project/issues/63012>`_)
793 - Fix handling of using-declarations in the init statements of for
795 (`#63627 <https://github.com/llvm/llvm-project/issues/63627>`_)
796 - Fix crash when emitting diagnostic for out of order designated initializers
798 (`#63605 <https://github.com/llvm/llvm-project/issues/63605>`_)
799 - Fix crash when using standard C++ modules with OpenMP.
800 (`#62359 <https://github.com/llvm/llvm-project/issues/62359>`_)
801 - Fix crash when using consteval non static data member initialization in
802 standard C++ modules.
803 (`#60275 <https://github.com/llvm/llvm-project/issues/60275>`_)
804 - Fix handling of ADL for dependent expressions in standard C++ modules.
805 (`#60488 <https://github.com/llvm/llvm-project/issues/60488>`_)
806 - Fix crash when combining `-ftime-trace` within standard C++ modules.
807 (`#60544 <https://github.com/llvm/llvm-project/issues/60544>`_)
808 - Don't generate template specializations when importing standard C++ modules.
809 (`#60693 <https://github.com/llvm/llvm-project/issues/60693>`_)
810 - Fix the visibility of `initializer list` in the importer of standard C++
811 modules. This addresses
812 (`#60775 <https://github.com/llvm/llvm-project/issues/60775>`_)
813 - Allow the use of constrained friend in standard C++ modules.
814 (`#60890 <https://github.com/llvm/llvm-project/issues/60890>`_)
815 - Don't evaluate initializer of used variables in every importer of standard
817 (`#61040 <https://github.com/llvm/llvm-project/issues/61040>`_)
818 - Fix the issue that the default `operator==` in standard C++ modules will
819 cause duplicate symbol linker error.
820 (`#61067 <https://github.com/llvm/llvm-project/issues/61067>`_)
821 - Fix the false positive ODR check for template names. This addresses the issue
822 that we can't include `<ranges>` in multiple module units.
823 (`#61317 <https://github.com/llvm/llvm-project/issues/61317>`_)
824 - Fix crash for inconsistent exported declarations in standard C++ modules.
825 (`#61321 <https://github.com/llvm/llvm-project/issues/61321>`_)
826 - Fix ignoring `#pragma comment` and `#pragma detect_mismatch` directives in
827 standard C++ modules.
828 (`#61733 <https://github.com/llvm/llvm-project/issues/61733>`_)
829 - Don't generate virtual tables if the class is defined in another module units
831 (`#61940 <https://github.com/llvm/llvm-project/issues/61940>`_)
832 - Fix false postive check for constrained satisfaction in standard C++ modules.
833 (`#62589 <https://github.com/llvm/llvm-project/issues/62589>`_)
834 - Serialize the evaluated constant values for variable declarations in standard
836 (`#62796 <https://github.com/llvm/llvm-project/issues/62796>`_)
837 - Merge lambdas in require expressions in standard C++ modules.
838 (`#63544 <https://github.com/llvm/llvm-project/issues/63544>`_)
840 - Fix location of default member initialization in parenthesized aggregate
842 (`#63903 <https://github.com/llvm/llvm-project/issues/63903>`_)
843 - Fix constraint checking of non-generic lambdas.
844 (`#63181 <https://github.com/llvm/llvm-project/issues/63181>`_)
846 - Update ``FunctionDeclBitfields.NumFunctionDeclBits``. This fixes:
847 (`#64171 <https://github.com/llvm/llvm-project/issues/64171>`_).
849 - Fix a crash caused by substitution failure in expression requirements.
850 (`#64172 <https://github.com/llvm/llvm-project/issues/64172>`_) and
851 (`#64723 <https://github.com/llvm/llvm-project/issues/64723>`_).
853 Bug Fixes to AST Handling
854 ^^^^^^^^^^^^^^^^^^^^^^^^^
856 - Preserve ``namespace`` definitions that follow malformed declarations.
858 Miscellaneous Bug Fixes
859 ^^^^^^^^^^^^^^^^^^^^^^^
861 Miscellaneous Clang Crashes Fixed
862 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
864 - Dumping the AST to JSON no longer causes a failed assertion when targetting
865 the Microsoft ABI and the AST to be dumped contains dependent names that
866 would not typically be mangled.
867 (`#61440 <https://github.com/llvm/llvm-project/issues/61440>`_)
869 Target Specific Changes
870 -----------------------
875 - Linking for AMDGPU now uses ``--no-undefined`` by default. This causes
876 undefined symbols in the created module to be a linker error. To prevent this,
877 pass ``-Wl,--undefined`` if compiling directly, or ``-Xoffload-linker
878 --undefined`` if using an offloading language.
879 - The deprecated ``-mcode-object-v3`` and ``-mno-code-object-v3`` command-line
880 options have been removed.
881 - A new option ``-mprintf-kind`` has been introduced that controls printf lowering
882 scheme. It is currently supported only for HIP and takes following values,
883 ``hostcall`` - printing happens during kernel execution via series of hostcalls,
884 The scheme requires the system to support pcie atomics.(default)
885 ``buffered`` - Scheme uses a debug buffer to populate printf varargs, does not
886 rely on pcie atomics support.
891 - Add ISA of ``AMX-COMPLEX`` which supports ``tcmmimfp16ps`` and
893 - Support ISA of ``SHA512``.
894 * Support intrinsic of ``_mm256_sha512msg1_epi64``.
895 * Support intrinsic of ``_mm256_sha512msg2_epi64``.
896 * Support intrinsic of ``_mm256_sha512rnds2_epi64``.
897 - Support ISA of ``SM3``.
898 * Support intrinsic of ``_mm_sm3msg1_epi32``.
899 * Support intrinsic of ``_mm_sm3msg2_epi32``.
900 * Support intrinsic of ``_mm_sm3rnds2_epi32``.
901 - Support ISA of ``SM4``.
902 * Support intrinsic of ``_mm(256)_sm4key4_epi32``.
903 * Support intrinsic of ``_mm(256)_sm4rnds4_epi32``.
904 - Support ISA of ``AVX-VNNI-INT16``.
905 * Support intrinsic of ``_mm(256)_dpwsud(s)_epi32``.
906 * Support intrinsic of ``_mm(256)_dpwusd(s)_epi32``.
907 * Support intrinsic of ``_mm(256)_dpwuud(s)_epi32``.
908 - ``-march=graniterapids-d`` is now supported.
910 Arm and AArch64 Support
911 ^^^^^^^^^^^^^^^^^^^^^^^
913 - The hard-float ABI is now available in Armv8.1-M configurations that
914 have integer MVE instructions (and therefore have FP registers) but
915 no scalar or vector floating point computation. Previously, trying
916 to select the hard-float ABI on such a target (via
917 ``-mfloat-abi=hard`` or a triple ending in ``hf``) would silently
918 use the soft-float ABI instead.
920 - Clang now emits ``-Wunsupported-abi`` if the hard-float ABI is specified
921 and the selected processor lacks floating point registers.
922 (`#55755 <https://github.com/llvm/llvm-project/issues/55755>`_)
924 - Clang builtin ``__arithmetic_fence`` and the command line option ``-fprotect-parens``
925 are now enabled for AArch64.
927 - Clang supports flag output operands by which conditions in the NZCV could be outputs
928 of inline assembly for AArch64. This change is more consistent with the behavior of
933 // int a = foo(); int* b = bar();
934 asm("ands %w[a], %w[a], #3" : [a] "+r"(a), "=@cceq"(*b));
936 - Fix a crash when ``preserve_all`` calling convention is used on AArch64.
937 `Issue 58145 <https://github.com/llvm/llvm-project/issues/58145>`_
939 - Clang now warns if invalid target triples ``--target=aarch64-*-eabi`` or
940 ``--target=arm-*-elf`` are specified.
948 - Patchable function entry (``-fpatchable-function-entry``) is now supported
950 - An ABI mismatch between GCC and Clang related to the handling of empty structs
951 in C++ parameter passing under ``lp64d`` ABI was fixed.
952 - Unaligned memory accesses can be toggled by ``-m[no-]unaligned-access`` or the
953 aliases ``-m[no-]strict-align``.
954 - Non ``$``-prefixed GPR names (e.g. ``r4`` and ``a0``) are allowed in inlineasm
956 - The ``-march=native`` ``-mtune=`` options and ``__loongarch_{arch,tune}``
957 macros are now supported.
961 - Added ``-mrvv-vector-bits=`` option to give an upper and lower bound on vector
962 length. Valid values are powers of 2 between 64 and 65536. A value of 32
963 should eventually be supported. We also accept "zvl" to use the Zvl*b
964 extension from ``-march`` or ``-mcpu`` to the be the upper and lower bound.
965 - Fixed incorrect ABI lowering of ``_Float16`` in the case of structs
966 containing ``_Float16`` that are eligible for passing via GPR+FPR or
968 - Removed support for ``__attribute__((interrupt("user")))``. User-level
969 interrupts are not in version 1.12 of the privileged specification.
970 - Added ``attribute(riscv_rvv_vector_bits(__riscv_v_fixed_vlen))`` to allow
971 the size of a RVV (RISC-V Vector) scalable type to be specified. This allows
972 RVV scalable vector types to be used in structs or in global variables.
973 - The rules for ordering of extensions in ``-march`` strings were relaxed. A
974 canonical ordering is no longer enforced on ``z*``, ``s*``, and ``x*``
976 - An ABI mismatch between GCC and Clang related to the handling of empty
977 structs in C++ parameter passing under the hard floating point calling
978 conventions was fixed.
979 - Support the RVV intrinsics v0.12. Please checkout `the RVV C intrinsics
981 <https://github.com/riscv-non-isa/rvv-intrinsic-doc/releases/tag/v0.12.0>`_.
982 It is expected there won't be any incompatibility from this v0.12 to the
983 specifications planned for v1.0.
985 * Added vector intrinsics that models control to the rounding mode
986 (``frm`` and ``vxrm``) for the floating-point instruction intrinsics and the
987 fixed-point instruction intrinsics.
988 * Added intrinsics for reinterpret cast between vector boolean and vector
990 * Removed the ``vread_csr`` and ``vwrite_csr`` intrinsics
991 - Default ``-fdebug-dwarf-version=`` is downgraded to 4 to work around
992 incorrect DWARF related to ULEB128 and linker compatibility before
993 ``R_RISCV_SET_ULEB128`` becomes more widely supported.
994 (`D157663 <https://reviews.llvm.org/D157663>`_).
996 CUDA/HIP Language Changes
997 ^^^^^^^^^^^^^^^^^^^^^^^^^
998 - Clang has been updated to align its default language standard for CUDA/HIP with
999 that of C++. The standard has now been enhanced to gnu++17, supplanting the
1000 previously used c++14.
1004 - Clang now supports CUDA SDK up to 12.1
1008 - Enabled ThinLTO support. Minimum OS requirement is AIX 7.2 TL5 SP7 or
1009 the upcoming AIX 7.3 TL2.
1011 - Enabled integrated assembler (``-f[no-]integrated-as``) for LTO. LTO now
1012 defaults to the integrated assembler.
1014 - Enabled Clang-based instrumented profiling
1015 (``-fprofile-instr-[generate|use]``).
1017 - Added an AIX-only link-time option, ``-mxcoff-build-id=0xHEXSTRING``, to allow
1018 users to embed a hex id in their binary such that it's readable by the program
1019 itself. This option is an alternative to the ``--build-id=0xHEXSTRING`` GNU
1020 linker option, which is currently not supported by the AIX linker.
1022 - Introduced the ``-mxcoff-roptr`` option to place constant objects with
1023 relocatable address values in the read-only data section. This option should
1024 be used with the ``-fdata-sections`` option, and is not supported with
1025 ``-fno-data-sections``. When ``-mxcoff-roptr`` is in effect at link time,
1026 read-only data sections with relocatable address values that resolve to
1027 imported symbols are made writable.
1029 - Implemented the ``-frecord-command-line`` option on AIX, which saves the
1030 command-line options used from compiling a source file to the corresponding
1031 object file or binary file.
1033 - Added a new linker option, ``-K``, that is used to align the header, text,
1034 data, and loader sections of the output file so that each section begins on
1039 - Shared library support (and PIC code generation) for WebAssembly is no longer
1040 limited to the Emscripten target OS and now works with other targets such as
1041 wasm32-wasi. Note that the `format
1042 <https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md>`_
1043 is not yet stable and may change between LLVM versions. Also, WASI does not
1044 yet have facilities to load dynamic libraries.
1048 - The definition of ``USHRT_MAX`` in the freestanding ``<limits.h>`` no longer
1049 overflows on AVR (where ``sizeof(int) == sizeof(unsigned short)``). The type
1050 of ``USHRT_MAX`` is now ``unsigned int`` instead of ``int``, as required by
1055 - Clang now emits errors when it detects incompatible target features for
1058 DWARF Support in Clang
1059 ----------------------
1061 Floating Point Support in Clang
1062 -------------------------------
1063 - Add ``__builtin_elementwise_log`` builtin for floating point types only.
1064 - Add ``__builtin_elementwise_log10`` builtin for floating point types only.
1065 - Add ``__builtin_elementwise_log2`` builtin for floating point types only.
1066 - Add ``__builtin_elementwise_exp`` builtin for floating point types only.
1067 - Add ``__builtin_elementwise_exp2`` builtin for floating point types only.
1068 - Add ``__builtin_set_flt_rounds`` builtin for X86, x86_64, Arm and AArch64 only.
1069 - Add ``__builtin_elementwise_pow`` builtin for floating point types only.
1074 - Add ``coroutineBodyStmt`` matcher.
1076 - The ``hasBody`` matcher now matches coroutine body nodes in
1077 ``CoroutineBodyStmts``.
1079 - Add ``arrayInitIndexExpr`` and ``arrayInitLoopExpr`` matchers.
1084 - Add ``NextLineOnly`` style to option ``PackConstructorInitializers``.
1085 Compared to ``NextLine`` style, ``NextLineOnly`` style will not try to
1086 put the initializers on the current line first, instead, it will try to
1087 put the initializers on the next line only.
1088 - Add additional Qualifier Ordering support for special cases such
1089 as templates, requires clauses, long qualified names.
1090 - Fix all known issues associated with ``LambdaBodyIndentation: OuterScope``.
1091 - Add ``BracedInitializerIndentWidth`` which can be used to configure
1092 the indentation level of the contents of braced init lists.
1093 - Add ``KeepEmptyLinesAtEOF`` to keep empty lines at end of file.
1094 - Add ``RemoveParentheses`` to remove redundant parentheses.
1095 - Add ``TypeNames`` to treat listed non-keyword identifiers as type names.
1096 - Add ``AlignConsecutiveShortCaseStatements`` which can be used to align case
1097 labels in conjunction with ``AllowShortCaseLabelsOnASingleLine``.
1098 - Add ``SpacesInParens`` style with ``SpacesInParensOptions`` to replace
1099 ``SpacesInConditionalStatement``, ``SpacesInCStyleCastParentheses``,
1100 ``SpaceInEmptyParentheses``, and ``SpacesInParentheses``.
1105 - Introduced the new function ``clang_CXXMethod_isExplicit``,
1106 which identifies whether a constructor or conversion function cursor
1107 was marked with the explicit identifier.
1109 - Introduced the new ``CXIndex`` constructor function
1110 ``clang_createIndexWithOptions``, which allows storing precompiled preambles
1111 in memory or overriding the precompiled preamble storage path.
1113 - Deprecated two functions ``clang_CXIndex_setGlobalOptions`` and
1114 ``clang_CXIndex_setInvocationEmissionPathOption`` in favor of the new
1115 function ``clang_createIndexWithOptions`` in order to improve thread safety.
1117 - Added check in ``clang_getFieldDeclBitWidth`` for whether a bit-field
1118 has an evaluable bit width. Fixes undefined behavior when called on a
1119 bit-field whose width depends on a template parameter.
1121 - Added ``CXBinaryOperatorKind`` and ``CXUnaryOperatorKind``.
1122 (`#29138 <https://github.com/llvm/llvm-project/issues/29138>`_)
1127 - Fix incorrect alignment attribute on the this parameter of certain
1128 non-complete destructors when using the Microsoft ABI.
1129 (`#60465 <https://github.com/llvm/llvm-project/issues/60465>`_)
1131 - Removed the deprecated
1132 ``consider-single-element-arrays-as-flexible-array-members`` analyzer option.
1133 Any use of this flag will result in an error.
1134 Use `-fstrict-flex-arrays=<n>
1135 <https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fstrict-flex-arrays>`_
1137 - Better modeling of lifetime-extended memory regions. As a result, the
1138 ``MoveChecker`` raises more true-positive reports.
1140 - Fixed some bugs (including crashes) around the handling of constant global
1141 arrays and their initializer expressions.
1143 - The ``CStringChecker`` will invalidate less if the copy operation is
1144 inferable to be bounded. For example, if the arguments of ``strcpy`` are
1145 known to be of certain lengths and that are in-bounds.
1154 // extent of 'arr' is 4, and writing "hi\n" (4 characters),
1155 // thus no buffer overflow can happen
1156 strcpy(x.arr, "hi\n");
1157 free(x.ptr); // no longer reports memory leak here
1159 Similarly, functions like ``strsep`` now won't invalidate the object
1160 containing the destination buffer, because it can never overflow.
1161 Note that, ``std::copy`` is still not modeled, and as such, it will still
1162 invalidate the enclosing object on call.
1163 (`#55019 <https://github.com/llvm/llvm-project/issues/55019>`_)
1165 - Implement ``BufferOverlap`` check for ``sprint``/``snprintf``
1166 The ``CStringChecker`` checks for buffer overlaps for ``sprintf`` and
1169 - Objective-C support was improved around checking ``_Nonnull`` and
1170 ``_Nullable`` including block pointers and literal objects.
1172 - Let the ``StreamChecker`` detect ``NULL`` streams instead of by
1173 ``StdCLibraryFunctions``.
1174 ``StreamChecker`` improved on the ``fseek`` modeling for the ``SEEK_SET``,
1175 ``SEEK_END``, ``SEEK_CUR`` arguments.
1177 - ``StdCLibraryFunctionArgs`` was merged into the ``StdCLibraryFunctions``.
1178 The diagnostics of the ``StdCLibraryFunctions`` was improved.
1180 - ``QTimer::singleShot`` now doesn't raise false-positives for memory leaks by
1181 the ``MallocChecker``.
1182 (`#39713 <https://github.com/llvm/llvm-project/issues/39713>`_)
1184 - Fixed the infamous unsigned index false-positives in the
1185 ``ArrayBoundCheckerV2`` checker.
1186 (`#44493 <https://github.com/llvm/llvm-project/issues/44493>`_)
1188 - Now, taint propagations are tracked further back until the real taint source.
1189 This improves all taint-related diagnostics.
1191 - Fixed a null-pointer dereference crash inside the ``MoveChecker``.
1193 .. _release-notes-sanitizers:
1197 - Several more sanitizers are now ported to LoongArch: MSan, DFsan, Profile, XRay and libFuzzer.
1199 Python Binding Changes
1200 ----------------------
1201 The following methods have been added:
1203 - ``clang_Location_isInSystemHeader`` exposed via the ``is_in_system_header``
1204 property of the `Location` class.
1206 Configurable Multilib
1207 ---------------------
1208 The BareMetal toolchain for AArch64 & ARM now supports multilib, configurable
1209 via ``multilib.yaml``. See `the multilib docs <https://clang.llvm.org/docs/Multilib.html>`_
1212 Additional Information
1213 ======================
1215 A wide variety of additional information is available on the `Clang web
1216 page <https://clang.llvm.org/>`_. The web page contains versions of the
1217 API documentation which are up-to-date with the Git version of
1218 the source code. You can access versions of these documents specific to
1219 this release by going into the "``clang/docs/``" directory in the Clang
1222 If you have any questions or comments about Clang, please feel free to
1223 contact us on the `Discourse forums (Clang Frontend category)
1224 <https://discourse.llvm.org/c/clang/6>`_.