[clang] Make the driver not diagnose errors on nonexistent linker inputs

When nonexistent linker inputs are passed to the driver, the linker
now errors out, instead of the compiler. If the linker does not run,
clang now emits a "warning: linker input unused" instead of an error
for nonexistent files.

The motivation for this change is that I noticed that
`clang-cl /winsysroot sysroot main.cc ole32.lib` emitted a
"ole32.lib not found" error, even though the linker finds it just fine when
I run `clang-cl /winsysroot sysroot main.cc /link ole32.lib`.

The same problem occurs if running `clang-cl main.cc ole32.lib` in a
non-MSVC shell.

The problem is that DiagnoseInputExistence() only looked for libs in %LIB%,
but MSVCToolChain uses much more involved techniques.

For this particular problem, we could make DiagnoseInputExistence() ask
the toolchain to see if it can find a .lib file, but in general the
driver can't know what the linker will do to find files, so it shouldn't
try. For example, if we implement PR24616, lld-link will look in the
registry to determine a good default for %LIB% if it isn't set.

This is less or a problem for the gcc driver, since .a paths there are
either passed via -l flags (which honor -L), or via a qualified path
(that doesn't honor -L) -- but for example ld.lld's --chroot flag
can also trigger this problem. Without this patch,
`clang -fuse-ld=lld -Wl,--chroot,some/dir /file.o` will complain that
`/file.o` doesn't exist, even though
`clang -fuse-ld=lld -Wl,--chroot,some/dir -Wl,/file.o` succeeds just fine.

This implements rnk's suggestion on the old bug PR27234.

Differential Revision: https://reviews.llvm.org/D109624

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 7dea484..50791ec 100644 (file)
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -2130,19 +2130,6 @@ bool Driver::DiagnoseInputExistence(const DerivedArgList &Args, StringRef Value,
   if (getVFS().exists(Value))
     return true;
 
-  if (IsCLMode()) {
-    if (!llvm::sys::path::is_absolute(Twine(Value)) &&
-        llvm::sys::Process::FindInEnvPath("LIB", Value, ';'))
-      return true;
-
-    if (Args.hasArg(options::OPT__SLASH_link) && Ty == types::TY_Object) {
-      // Arguments to the /link flag might cause the linker to search for object
-      // and library files in paths we don't know about. Don't error in such
-      // cases.
-      return true;
-    }
-  }
-
   if (TypoCorrect) {
     // Check if the filename is a typo for an option flag. OptTable thinks
     // that all args that are not known options and that start with / are
@@ -2162,6 +2149,34 @@ bool Driver::DiagnoseInputExistence(const DerivedArgList &Args, StringRef Value,
     }
   }
 
+  // Don't error on apparently non-existent linker inputs, because they
+  // can be influenced by linker flags the clang driver might not understand.
+  // Examples:
+  // - `clang -fuse-ld=lld -Wl,--chroot,some/dir /file.o` will make lld look
+  //   for some/dir/file.o
+  // - `clang-cl main.cc ole32.lib` in a a non-MSVC shell will make the driver
+  //   module look for an MSVC installation in the registry. (We could ask
+  //   the MSVCToolChain object if it can find `ole32.lib`, but the logic to
+  //   look in the registry might move into lld-link in the future so that
+  //   lld-link invocations in non-MSVC shells just work too.)
+  // - `clang-cl ... /link ...` can pass arbitrary flags to the linker,
+  //   including /libpath:, which is used to find .lib and .obj files.
+  // So do not diagnose this on the driver level. Rely on the linker diagnosing
+  // it. (If we don't end up invoking the linker, this means we'll emit a
+  // "'linker' input unused [-Wunused-command-line-argument]" warning instead
+  // of an error.)
+  //
+  // Only do this skip after the typo correction step above. `/Brepo` is treated
+  // as TY_Object, but it's clearly a typo for `/Brepro`. It seems fine to emit
+  // an error if we have a flag that's within an edit distance of 1 from a
+  // flag. (Users can use `-Wl,` or `/linker` to launder the flag past the
+  // driver in the unlikely case they run into this.)
+  //
+  // Don't do this skip in clang-cl mode for inputs that start with a '/' --
+  // else we'd pass options like /libpath: through to the linker silently.
+  if (Ty == types::TY_Object && !(IsCLMode() && Value.startswith("/")))
+    return true;
+
   Diag(clang::diag::err_drv_no_such_file) << Value;
   return false;
 }

diff --git a/clang/test/Driver/cl-inputs.c b/clang/test/Driver/cl-inputs.c
index 35e4fbf..2b9d559 100644 (file)
--- a/clang/test/Driver/cl-inputs.c
+++ b/clang/test/Driver/cl-inputs.c
@@ -55,9 +55,9 @@
 // LIBINPUT: "cl-test.lib"
 
 // RUN: env LIB=%S/Inputs/cl-libs %clang_cl -fuse-ld=link -### -- %s cl-test2.lib 2>&1 | FileCheck -check-prefix=LIBINPUT2 %s
-// LIBINPUT2: error: no such file or directory: 'cl-test2.lib'
+// LIBINPUT2-NOT: error: no such file or directory: 'cl-test2.lib'
 // LIBINPUT2: link.exe"
-// LIBINPUT2-NOT: "cl-test2.lib"
+// LIBINPUT2: "cl-test2.lib"
 
 // RUN: %clang_cl -fuse-ld=link -### -- %s /nonexisting.lib 2>&1 | FileCheck -check-prefix=LIBINPUT3 %s
 // LIBINPUT3: error: no such file or directory: '/nonexisting.lib'

diff --git a/clang/test/Driver/cl-link.c b/clang/test/Driver/cl-link.c
index e2f5397..dcb7801 100644 (file)
--- a/clang/test/Driver/cl-link.c
+++ b/clang/test/Driver/cl-link.c
@@ -47,12 +47,20 @@
 // DEBUG: link.exe
 // DEBUG: "-debug"
 
+// Don't pass through /libpath: if it's not after a /link flag:
+// RUN: %clang_cl /Tc%s /libpath:foo -fuse-ld=link -### /link /libpath:bar 2>&1 | FileCheck --check-prefix=LIBPATH %s
+// LIBPATH: error: no such file or directory: '/libpath:foo'
+// LIBPATH: libpath:bar
+
 // PR27234
 // RUN: %clang_cl /Tc%s nonexistent.obj -fuse-ld=link -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
 // RUN: %clang_cl /Tc%s nonexistent.lib -fuse-ld=link -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.obj -fuse-ld=link -### /winsysroot somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.lib -fuse-ld=link -### /winsysroot somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.obj -fuse-ld=link -### 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.lib -fuse-ld=link -### 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
 // NONEXISTENT-NOT: no such file
 // NONEXISTENT: link.exe
-// NONEXISTENT: "/libpath:somepath"
 // NONEXISTENT: nonexistent
 
 // RUN: %clang_cl /Tc%s -fuse-ld=lld -### 2>&1 | FileCheck --check-prefix=USE_LLD %s

diff --git a/clang/test/Driver/unknown-arg.c b/clang/test/Driver/unknown-arg.c
index 0e3e5bf..75ae18f 100644 (file)
--- a/clang/test/Driver/unknown-arg.c
+++ b/clang/test/Driver/unknown-arg.c
@@ -10,6 +10,8 @@
 // RUN:     FileCheck %s --check-prefix=CL-DID-YOU-MEAN
 // RUN: %clang_cl /Brepo -### -- %s 2>&1 | \
 // RUN:     FileCheck %s --check-prefix=CL-DID-YOU-MEAN-SLASH
+// RUN: %clang_cl /Brepo -### /Tc%s /link 2>&1 | \
+// RUN:     FileCheck %s --check-prefix=CL-DID-YOU-MEAN-SLASH
 // RUN: not %clang_cl -cake-is-lie -%0 -%d -HHHH -munknown-to-clang-option -print-stats -funknown-to-clang-option -c -Werror=unknown-argument -### -- %s 2>&1 | \
 // RUN:     FileCheck %s --check-prefix=CL-ERROR
 // RUN: not %clang_cl -helo -Werror=unknown-argument -### -- %s 2>&1 | \

diff --git a/flang/test/Driver/missing-input.f90 b/flang/test/Driver/missing-input.f90
index d9d444e..44ee6d8 100644 (file)
--- a/flang/test/Driver/missing-input.f90
+++ b/flang/test/Driver/missing-input.f90
@@ -9,12 +9,12 @@
 ! FLANG DRIVER (flang-new)
 !--------------------------
 ! RUN: not %flang  2>&1 | FileCheck %s --check-prefix=FLANG-NO-FILE
-! RUN: not %flang %t 2>&1 | FileCheck %s --check-prefix=FLANG-NONEXISTENT-FILE
+! RUN: not %flang %t.f90 2>&1 | FileCheck %s --check-prefix=FLANG-NONEXISTENT-FILE
 
 !-----------------------------------------
 ! FLANG FRONTEND DRIVER (flang-new -fc1)
 !-----------------------------------------
-! RUN: not %flang_fc1 %t 2>&1  | FileCheck %s --check-prefix=FLANG-FC1-NONEXISTENT-FILE
+! RUN: not %flang_fc1 %t.f90 2>&1  | FileCheck %s --check-prefix=FLANG-FC1-NONEXISTENT-FILE
 ! RUN: not %flang_fc1 %S 2>&1  | FileCheck %s --check-prefix=FLANG-FC1-DIR
 
 !-----------------------