[clang] 837f998 - [clang-cl] Don't count linker inputs against /Fo and /Fa (#232611)

[via cfe-commits]

Author: Haohai Wen
Date: 2026-10-21T10:46:37+08:00
New Revision: 837f998d417a92ba9b56998e532454715749479f

URL: https://github.com/llvm/llvm-project/commit/837f998d417a92ba9b56998e532454715749479f
DIFF: https://github.com/llvm/llvm-project/commit/837f998d417a92ba9b56998e532454715749479f.diff

LOG: [clang-cl] Don't count linker inputs against /Fo and /Fa (#232611)

The /Fo and /Fa checks reject a file name when there is more than one
input. But the input list also holds object files, libraries, and linker
options such as -Xlinker, which go straight to the linker and never get
an output named by /Fo or /Fa. So

  clang-cl /c foo.c /Fofoo.obj -Xlinker -bar

failed with "cannot specify '/Fofoo.obj' when compiling multiple source
files". MSVC's cl.exe also accepts .obj and .lib inputs next to
/Fo<file>.

Count only the inputs that get compiled.

Fixes #216085.

Added: 
    

Modified: 
    clang/lib/Driver/Driver.cpp
    clang/test/Driver/cl-outputs.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 1c612c7d1547b..75471cfb63dd0 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -3387,27 +3387,25 @@ void Driver::handleArguments(Compilation &C, DerivedArgList &Args,
                              const InputList &Inputs,
                              ActionList &Actions) const {
 
-  // Diagnose misuse of /Fo.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fo)) {
-    StringRef V = A->getValue();
-    if (Inputs.size() > 1 && !V.empty() &&
-        !llvm::sys::path::is_separator(V.back())) {
-      // Check whether /Fo tries to name an output file for multiple inputs.
-      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
-          << A->getSpelling() << V;
-      Args.eraseArg(options::OPT__SLASH_Fo);
-    }
-  }
-
-  // Diagnose misuse of /Fa.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fa)) {
-    StringRef V = A->getValue();
-    if (Inputs.size() > 1 && !V.empty() &&
-        !llvm::sys::path::is_separator(V.back())) {
-      // Check whether /Fa tries to name an asm file for multiple inputs.
-      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
-          << A->getSpelling() << V;
-      Args.eraseArg(options::OPT__SLASH_Fa);
+  // Diagnose misuse of /Fo and /Fa.
+  if (Arg *FoArg = Args.getLastArg(options::OPT__SLASH_Fo),
+      *FaArg = Args.getLastArg(options::OPT__SLASH_Fa);
+      FoArg || FaArg) {
+    // Linker inputs do not produce the outputs named by /Fo and /Fa.
+    unsigned NumCompiledInputs = llvm::count_if(
+        Inputs, [](const InputTy &I) { return I.first != types::TY_Object; });
+
+    for (Arg *A : {FoArg, FaArg}) {
+      if (!A)
+        continue;
+      StringRef V = A->getValue();
+      if (NumCompiledInputs > 1 && !V.empty() &&
+          !llvm::sys::path::is_separator(V.back())) {
+        // Check whether /Fo or /Fa names an output file for multiple inputs.
+        Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
+            << A->getSpelling() << V;
+        Args.eraseArg(A->getOption().getID());
+      }
     }
   }
 

diff  --git a/clang/test/Driver/cl-outputs.c b/clang/test/Driver/cl-outputs.c
index c59adc8acb3b6..b480f62897214 100644
--- a/clang/test/Driver/cl-outputs.c
+++ b/clang/test/Driver/cl-outputs.c
@@ -37,6 +37,11 @@
 // CHECK-MULTIPLESOURCEOK2: "-o" "cl-outputs.obj"
 // CHECK-MULTIPLESOURCEOK2: "-o" "cl-outputs.obj"
 
+// RUN: %clang_cl /c /Foa.obj -Xlinker -foo -### -- %s foo.obj foo.lib 2>&1 | FileCheck -check-prefix=FoLINKERINPUT %s
+// RUN: %clang_cl /Foa.obj -Xlinker -foo -### -- %s foo.lib 2>&1 | FileCheck -check-prefix=FoLINKERINPUT %s
+// FoLINKERINPUT-NOT: error: cannot specify '/Foa.obj' when compiling multiple source files
+// FoLINKERINPUT: "-o" "a.obj"
+
 // RUN: %clang_cl /c /oa -### -- %s 2>&1 | FileCheck -check-prefix=oNAME1 %s
 // oNAME1:  "-o" "a.obj"
 
@@ -243,6 +248,9 @@
 // RUN: %clang_cl /Fa -### -- %s %s 2>&1 | FileCheck -check-prefix=FaMULTIPLESOURCEOK %s
 // FaMULTIPLESOURCEOK: "-o" "cl-outputs.asm"
 // FaMULTIPLESOURCEOK: "-o" "cl-outputs.asm"
+// RUN: %clang_cl /Faa.asm -Xlinker -foo -### -- %s foo.obj 2>&1 | FileCheck -check-prefix=FaLINKERINPUT %s
+// FaLINKERINPUT-NOT: error: cannot specify '/Faa.asm' when compiling multiple source files
+// FaLINKERINPUT: "-o" "a.asm"
 
 // Copy of the same tests above, but with /FAcsu
 // RUN: %clang_cl /FAcsu -### -- %s 2>&1 | FileCheck -check-prefix=FA_CSU %s