3 * Experimental support for linker garbage collection (--gc-sections)
4 has been enabled for COFF and PE based targets.
6 * New command line option for ELF targets to compress DWARF debug
7 sections, --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi].
9 * New command line option, --orphan-handling=[place|warn|error|discard], to
10 adjust how orphan sections are handled. The default is 'place' which gives
11 the current behaviour, 'warn' and 'error' issue a warning or error
12 respectively when orphan sections are found, and 'discard' will discard all
15 * Add support for LLVM plugin.
17 * Add --print-memory-usage option to report memory blocks usage.
19 * Add --require-defined option, it's like --undefined except the new symbol
20 must be defined by the end of the link.
24 * PE binaries now once again contain real timestamps by default. To disable
25 the inclusion of a timestamp in a PE binary, use the --no-insert-timestamp
28 * Replace support for openrisc and or32 with support for or1k.
30 * Add support for the --build-id command line option to COFF based targets.
32 * x86/x86_64 pe-coff now supports the --build-id option.
34 * Add support for the Andes NDS32.
38 * Add LOG2CEIL() builtin function to the linker script language
40 * Add support for the Texas Instruments MSP430X processor.
42 * Add support for Altera Nios II.
44 * Add support for the V850E3V5 architecture.
46 * Add support for the Imagination Technologies Meta processor.
48 * --enable-new-dtags no longer generates old dtags in addition to new dtags.
50 * Remove linker support for MIPS ECOFF targets.
52 * Add ALIGN_WITH_INPUT to the linker script language to force the alignment of
53 an output section to use the maximum alignment of all its input sections.
57 * Enable compressed debug section feature for x86/x86_64 pe-coff.
59 * Add support for the 64-bit ARM architecture: AArch64.
61 * Added SORT_NONE to the linker script language to disable section sorting.
63 * Add a linker-provided symbol when producing ELF output, '__ehdr_start'
64 to point to the ELF file header (and nearby program headers) in the
65 program's memory image.
67 * Add support for S12X processor.
69 * Add support for the VLE extension to the PowerPC architecture.
71 * Add support for the Freescale XGATE architecture.
73 * Add option -f FILE on AIX (for response file).
75 * Add support for the Renesas RL78 architecture.
77 * Add support for the Adapteva EPIPHANY architecture.
81 * --copy-dt-needed-entries is no longer enabled by default. Instead
82 --no-copy-dt-needed-entries is the default.
84 * INPUT_SECTION_FLAGS has been added to the linker script language
85 to allow selection of input sections by section header section flags.
87 * Add support for the Tilera TILEPro and TILE-Gx architectures.
89 * Added SORT_BY_INIT_PRIORITY to the linker script language to permit
90 sorting sections by numerical value of the GCC init_priority attribute
91 encoded in the section name.
95 * Linker script expression evaluation is somewhat more sane. This may
96 break scripts that depend on quirks of the old expression evaluation.
98 * Turn off underscoring for x86_64 PE+-COFF targets. For old behavior the
99 option --enable-leading-mingw64-underscores can be used on configure of
102 * Add support for the TMS320C6000 (TI C6X) processor family.
104 * --add-needed renamed to --copy-dt-needed-entries in order to avoid confusion
105 with --as-needed option.
107 * Extend .def file syntax by '== <ID>' for imports and exports. This allows
108 to alias the import/export table name written in PE image.
110 * Add --exclude-all-symbols option to PE based linkers. This prevents all
111 symbols from automatically being exported.
113 * Add support for the Renesas RX processor.
115 * Add support for alpha-vms target.
119 * GNU/Linux targets now support the STB_GNU_UNIQUE symbol binding. This is a
120 GNU extension to the standard set of ELF symbol bindings. The binding will
121 be passed on to the dynamic linker which will make sure that in the entire
122 process there is just one symbol with the given name and type in use.
124 * PE targets now support a GNU extension to allow the alignment of common
125 common symbols to be specified. This support uses custom options in
126 the .drectve section, which will be disregarded by the native tools.
128 * PE targets now add primitive support for ELF version scripts; symbols
129 are not versioned, but the local and global symbol visibility directives
130 are respected when filtering symbols in auto-export mode.
132 * New option --no-export-dynamic to undo the effect of the -E and
133 --export-dynamic options.
135 * ELF: --warn-alternate-em option to warn if an object has alternate
138 * New script function REGION_ALIAS to add alias names to memory regions.
140 * PE targets no longer make use of the long section names PE extension to
141 the COFF format when generating executable images, by default. The old
142 (slightly non-conformant) behaviour can still be invoked by using the
143 new '--enable-long-section-names' command-line option. It is also enabled
144 automatically in the presence of un-stripped debug information, as GDB
145 needs to be able to find the debug info sections by their full names.
147 * For GNU/Linux systems the linker will now avoid processing any relocations
148 made against symbols of the STT_GNU_IFUNC type and instead emit them into
149 the resulting binary for processing by the loader.
151 * --as-needed now links in a dynamic library if it satisfies undefined
152 symbols in regular objects, or in other dynamic libraries. In the
153 latter case the library is not linked if it is found in a DT_NEEDED
154 entry of one of the libraries already linked.
156 * Add a new command line option, -Ttext-segment ADDR, for ELF targets
157 to set the address of the first byte of the text segment.
159 * Add support for Sunplus score architecture.
161 * Add new option --use-nul-prefixed-import-tables to ld for PE targets to
162 allow fallback to old import table generation with null element prefix.
164 * Windows PE systems now support a new --exclude-modules-for-implib option,
165 allowing users to partition object files and archive members between a DLL
166 and its associated import library as they are generated during linking.
168 * Add support for Lattice Mico32 (lm32) architecture.
170 * Add CR16 ELF --embedded-relocs (used to embedded relocations into binaries
171 for Embedded-PIC code) option.
173 * Add to the PE/PE+ targets the support of two different kinds of
174 pseudo-relocations. They can be selected by the switches
175 --enable-runtime-pseudo-reloc-v1 and --enable-runtime-pseudo-reloc-v2.
176 For the switch --enable-runtime-pseudo-reloc it uses for 32-bit
177 runtime pseudo relocation version one, for 64-bit the version two.
181 * Linker scripts support a new INSERT command that makes it easier to
182 augment the default script.
184 * Linker script input section filespecs may now specify a file within an
185 archive by writing "archive:file".
187 * The --sort-common switch now has an optional argument which specifies the
188 direction of sorting.
190 * The M68K linker now supports multiple GOT generation schemes controlled via
191 the --got=<type> command line option.
193 * The ARM EABI linker will now generate stubs for function calls to symbols
194 that are too far away. The placement of the stubs is controlled by a new
195 linker command line option: --stub-group-size=N.
199 * Linker sources now released under version 3 of the GNU General Public
202 * ELF: New --build-id option to generate a unique per-binary identifier
203 embedded in a note section.
205 * Added support for National Semicondutor CompactRISC (ie CR16) target.
207 * -l:foo now searches the library path for a filename called foo,
208 without converting it to libfoo.a or libfoo.so.
210 * Add a new command line option '--default-script=FILE' or '-dT FILE'
211 which specifies a replacement for the built in, default linker
214 * ELF: Add -Bsymbolic-functions, --dynamic-list-cpp-new, which puts C++
215 operator new and delete on the dynamic list, and --dynamic-list-data,
216 builtin list for --dynamic-list, which puts global data symbols on the
219 * Add support for x86_64 PE+ target.
221 * Add support for Score target.
223 * ELF: Add --dynamic-list option to specify a list of global symbols
224 whose references shouldn't be bound to the definition within the
225 shared library, or a list of symbols which should be added to the
226 symbol table in the executable.
228 * The default output section LMA has changed for allocatable sections from
229 being equal to VMA, to keeping the difference between LMA and VMA the same as
230 the previous output section in the same region. This is a more useful
231 default when using overlays and other cases where you specify an LMA
232 differing from the VMA for some sections.
234 * New switch: --print-gc-sections to list any sections removed by garabge
237 * ARM: Added --vfp11-denorm-fix option to work around an erratum in current
242 * Support for the Infineon XC16X has been added by KPIT Cummins Infosystems.
244 * Modify the Linux linker search order to better match ld.so search order.
245 Look for DT_NEEDED libraries in paths specified by ld.so.conf before
246 searching the default directories, rather than vice versa.
247 Use $prefix/etc/ld.so.conf if it exists, otherwise /etc/ld.so.conf.
249 * PE-COFF: Forward exports from DLL's can now be specified in .def files
250 passed directly to ld.
252 * Support for the Z80 processor family has been added.
254 * Add support for the "@<file>" syntax to the command line, so that extra
255 switches can be read from <file>.
259 * Support for the R_ARM_V4BX relocation as defined in the ARM AAELF
260 specification has been added via the --fix-v4bx command-line option.
262 * New linker script construct AS_NEEDED(), which sets the --as-needed flag
263 for input files listed inside of it.
265 * A new command-line option, --sysroot, can be used to override the
266 default sysroot location. It only applies to toolchains that were
267 configured using --with-sysroot.
269 * New linker script functions: ORIGIN() and LENGTH() which return information
270 about a specified memory region.
272 * Port to MAXQ processor contributed by HCL Tech.
274 * Added SEGMENT_START to the linker script language to permit the user to
275 override the base address for a segment from the command-line.
277 * ELF: --warn-shared-textrel option to warn if adding a DT_TEXTREL to a shared
280 * Added SORT_BY_NAME and SORT_BY_ALIGNMENT to the linker script
281 language to permit sorting sections by section name or section
284 * Added a new linker command line switch, --sort-section name|alignment,
285 to sort sections by section name or maximum alignment.
287 * ELF: --add-needed/--no-add-needed options to control if a DT_NEEDED tag
288 should be added when a shared library comes from DT_NEEDED tags.
290 * Support for the crx-elf target added.
292 * Support for the sh-symbianelf target added.
294 * A new linker command line switch has been added which allows the hash table
295 size to be set to a suitable prime value near to its argument. This switch
296 is --hash-size=<NUMBER>. Also if the switch --reduce-memory-overheads is
297 used, and --hash-size has not been used, then the default value will be set
300 * Linker map files are now generated with an O(N) algorithm for finding symbols
301 that are defined in each section. This uses about 40% more memory for
302 symbols than the old O(N^2) algorithm. You can use the new
303 --reduce-memory-overheads option to select the old algorithm; this option
304 might also be used in the future to select similar tradeoffs.
308 * ELF: --as-needed/--no-as-needed options to control if a DT_NEEDED tag should
309 be added only when a shared library is referenced.
311 * PE: --large-address-aware option to indicate executables support virtual
312 addresses greater than 2 gigabytes.
314 * DWARF 2 support for i386pe added.
316 * The linker script operator DEFINED() will now yield 1 only for a symbol that
317 is defined before the statement where DEFINED is used.
319 * The MIPS --embedded-relocs (used to embed relocations into binaries for
320 Embedded-PIC code) is deprecated and will be removed in a future release.
322 * cr16c support added by NSC.
324 * m32r Linux (ELF) support added by Renesas.
326 * Improved linker's handling of unresolved symbols. The switch
327 --unresolved-symbols=<method> has been added to tell the linker when it
328 should report them and the switch --warn-unresolved-symbols has been added to
329 make reports be issued as warning messages rather than errors.
333 * Added support for Xtensa architecture.
335 * Added --with-sysroot configure switch to specify a target system root, for
336 linking against a target filesystem image.
338 * Added --accept-unknown-linker-format to restore old linker behaviour (pre
339 2.14) of silently accepting and linking in any files in an unknown binary
342 * Added --no-omagic to undo the effects of the -N option.
344 * Support for Texas Instruments TMS320C4x and TMS320C3x series of
345 DSP's contributed by Michael Hayes and Svein E. Seldal.
347 * Added --with-lib-path configure switch to specify default value for
350 * ARM port to QNX operating system added by Graeme Peterson.
352 * IP2K support added by Denis Chertykov.
356 * Support for the Fujitsu FRV architecture added by Red Hat. Models for FR400
359 Changes in version 2.13:
361 * DEC VAX ELF support, by Matt Thomas.
363 Changes in version 2.12:
365 * Support for Don Knuth's MMIX, by Hans-Peter Nilsson.
367 * Support for the OpenRISC 32-bit embedded processor by OpenCores.
369 * Support for -z nocopyreloc in the x86 ELF linker, which disables
370 production of copy relocs. Warning: using this option may result in
371 non-sharable applications.
373 * Support for -z combreloc in the ELF linker, which puts dynamic
374 relocations against the same symbol together, so that dynamic linker
375 can use an one-entry symbol lookup cache.
377 * Support for ELF SHF_MERGE section merging, by Jakub Jelinek.
379 Changes in version 2.11:
381 * Support for AMD x86-64 architecture, by Jan Hubicka, SuSE Labs.
383 * Support added for eliminating duplicate DWARF2 debug information by
384 having the compiler generate the information in sections called
385 .gnu.linkonce.wi.XXXX where XXXX is a checksum for the contents. The
386 linker then merges these sections together into the normal .debug_info
389 * The native ELF linker now searches the directories in DT_RUNPATH or
390 DT_RPATH of a shared library for shared libraries needed by it.
392 * TI C54x support, by Timothy Wall.
394 * Added command line switch --section-start to set the start address of any
397 * Added ability to emit full relocation information in linked executables,
398 enabled by --emit-relocs. Some post-linkage optimization tools need
399 this information in order to be able to correctly identify and perform
400 symbol relative addressing in the event of changes in section contents
401 (instructions being added or deleted, extending data sections, etc.)
403 * Support for i860, by Jason Eckhardt (preliminary, alpha quality).
405 * Support for CRIS (Axis Communications ETRAX series).
407 * Support for PDP-11 and 2.11BSD a.out format, by Lars Brinkhoff.
409 Changes in version 2.10:
411 * Added AT> to the linker script language to allow load-time allocation of
412 sections into regions.
414 * Added garbage collection of unused sections, enabled by --gc-sections.
415 It does require a bit of backend support; currently implemented are
416 arm-elf, avr-elf, d10v-elf, fr30-elf, i386-elf, m32r-elf, m68k-elf,
417 mcore-elf, mips-elf, mn10300-elf, ppc-elf, sh-elf, sparc-elf, and v850-elf.
418 Others will ignore the option.
420 * Added SORT to the linker script language to permit sorting sections by file
421 name or section name.
423 * Added EXTERN to the linker script language as an equivalent to the -u
426 * Added ASSERT to the linker script language.
428 * Added EXCLUDE_FILE to the linker script language for further control over
431 * Added -O option to optimize linker output (as of this writing, this only
432 affects ELF shared library generation).
434 * The -e option now accepts a number as well as a symbol name.
436 * Added --no-undefined option to disallow undefined symbols when creating a
439 * The linker now issues a warning, not an error, for an undefined symbol when
440 using -Bsymbolic; use the new --no-undefined option to get the old
443 * Added --demangle and --no-demangle options.
445 Changes in version 2.9:
447 * Added SQUAD to the linker script language.
449 * New option --no-warn-mismatch.
451 * The MEMORY command now parses the attributes to determine where sections that
452 are not placed in a specific memory region are placed.
454 Changes in version 2.8:
456 * Linker scripts may now contain shell wildcard characters for file and section
459 * The linker now supports symbol versions in ELF.
461 * The NOCROSSREFS command was added to the linker script language.
463 * The LOADADDR expression was added to the linker script language.
465 * MAX and MIN functions were added to the linker script language.
467 * The OVERLAY construct was added to the linker script language.
469 * New option --warn-section-align to warn when the address of an output section
470 changes due to alignment of an input section.
472 * New options --filter/-F and --auxiliary/-f.
474 Changes in version 2.7:
476 * New option --cref to print out a cross reference table.
478 * New option --wrap SYMBOL.
480 * New option --no-whole-archive, to turn off the effect of --whole-archive.
482 * Input sections assigned to the output section /DISCARD/ in the linker script
483 are not included in the output file.
485 * The SunOS and ELF linkers now merge stabs debugging information which uses
486 the N_BINCL and N_EINCL stab types. This reduces the amount of debugging
487 information generated.
489 Changes in version 2.6:
491 * When an ELF section name is representable as a C identifier (this is not true
492 of most ELF section names), the linker will automatically define symbols
493 __start_SECNAME and __stop_SECNAME, where SECNAME is the section name, at the
494 beginning and the end of the section. This is used by glibc.
496 Addendum: Current versions of the linker (at least for version 2.18 onwards
497 and possibly much earlier as well) place two restrictions on this feature: The
498 symbols are only implemented for orphaned sections, not for explicitly placed
499 sections and they are PROVIDEd rather than being defined.
501 * When an ELF section named .gnu.warning is encountered in an input file, the
502 contents of the section are displayed as an error message, and the section is
503 not copied into the output file. This is used by glibc.
505 * When an ELF section named .gnu.warning.SYMBOL is encountered in an input
506 file, and the symbol SYMBOL is referenced by some object file, the contents of
507 the section are displayed as an error message. The section is not copied into
508 the output file, unless doing a relocatable or shared link. This is used by
511 * New options -split-by-reloc and -split-by-file.
513 * The linker now supports linking PIC compiled code on SPARC SunOS. It can
514 also create SPARC SunOS shared libraries, and, like the native SunOS linker,
515 will do so whenever there is an undefined symbol in the link and neither the -e
516 nor the -r option was used.
518 * The -rpath option may be used on SunOS to set the list of directories to be
519 searched at run time. This overrides the default of building the list from the
522 * The COFF linker now combines debugging information for structs, unions, and
523 enums, so that even if the same type is defined in multiple input files it will
524 only be defined once in the output file. The --traditional-format switch will
525 prevent this optimization.
527 Changes in version 2.5:
529 * The linker now supports linking against SunOS shared libraries. It still can
530 not link SunOS PIC (Position Independent Code) files, so it can not be used to
531 generate shared libraries.
533 * The linker now supports linking against ELF shared libraries for the i386
534 (UnixWare) and SPARC (Solaris). It can also link ELF PIC files, and can be
535 used to generate shared libraries. Shared library generation is not well
536 tested; please report any problems encountered. The linker is now enabled for
539 * Eric Youngdale has contributed Linux support code, including linking against
540 Linux a.out shared libraries. The linker produces Linux QMAGIC binaries.
542 * The ELF backend has been converted to the new linker code. To use the new
543 ELF linker, each particular target requires a relocation function. So far,
544 this function has been written for i386 (UnixWare), SPARC (Solaris) MIPS (Irix
545 5), and HPPA ELF targets.
547 * The -( (--start-group) and -) (--end-group) options have been added to
548 support searching a group of archives as though they were a single archive.
549 This can also be used in a linker script, as GROUP ( files ).
551 * When a file is named on the command line, and the linker does not recognize
552 it as an object file, the linker will now treat the file as a linker script
553 file. A linker script named in this way augments, but does not replace, the
554 default linker script.
556 * The -warn-once option was added. It causes the linker to only warn once per
557 undefined symbol, rather than once per reference.
559 * The COFF backend has been converted to the new linker code. As with ELF, to
560 use the new linker, each particular target requires a relocation function. So
561 far, this function has been written for the i386, m68k, a29k and SH targets.
563 * The -V flag was made a synonym for -v, for SVR4 compatibility. The old -V
564 behaviour is available via --verbose.
566 Changes in version 2.4:
568 * New linker code, by Steve Chamberlain and Ian Taylor. For a.out and ecoff
569 formats (so far), this should result in considerable savings in time
570 and memory used while linking; slightly poorer performance than
571 before for formats not converted yet.
573 * Command-line parsing is no longer done with flex. This means
574 oddball characters in filenames won't get treated as argument
577 * HP-PA ELF support, by Jeff Law. (No SOM support yet.)
579 * Mach i386 support, by David Mackenzie.
581 * Irix 4 shared libraries are now supported (Irix 5 uses ELF, and ELF shared
582 libraries are not yet supported).
584 * COFF shared libraries (as on SCO) should work as well.
586 * The linker is disabled for Solaris. (Actually, it was in 2.3 also, I just
587 forgot to note it.) Some of their C library routines don't work when
588 statically linked, and the GNU linker doesn't support dynamic linking yet.
590 Changes in version 2.3:
592 * Weak symbols are now supported.
594 * ELF support has been added. The linker has been bootstrapped on
595 UnixWare and Solaris.
597 * Alpha OSF/1 support has been added (non dynamic linking only).
599 Changes in version 2.2:
601 * The `bfd' library has been updated to reduce a.out-format string
602 table size. The effect of this is that files linked from many input
603 files with duplicate symbols (`-g' debugging records, or identical
604 static symbols) should be much smaller.
606 Changes in version 2.1:
608 * The ld -ySYMBOL flag (to trace references to SYMBOL) is now implemented.
610 * There is now support for writing ECOFF files, so ld and the
611 other utilities should work on Risc/Ultrix and Irix.
614 Copyright (C) 2012-2015 Free Software Foundation, Inc.
616 Copying and distribution of this file, with or without modification,
617 are permitted in any medium without royalty provided the copyright
618 notice and this notice are preserved.