Author: Aaron Ballman
Date: 2025-11-04T08:17:50-05:00
New Revision: 2e89b71906307d7394be503e07939a42d4449d51

URL: 
https://github.com/llvm/llvm-project/commit/2e89b71906307d7394be503e07939a42d4449d51
DIFF: 
https://github.com/llvm/llvm-project/commit/2e89b71906307d7394be503e07939a42d4449d51.diff

LOG: [C23] Correctly handle missing embed with -MG (#166188)

-MG is supposed to suppress "file not found" diagnostics and instead
treat those as generated files for purposes of dependency scanning.
Clang was previously emitting the diagnostic instead of emitting the
name of the embedded file.

Fixes #165632

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Frontend/DependencyFile.cpp
    clang/lib/Lex/PPDirectives.cpp
    clang/test/Driver/mg.c

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2e2c5198fa8f5..3f57ddc92d5e8 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -209,6 +209,8 @@ C23 Feature Support
   `WG14 N2710 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2710.htm>`_.
 - Fixed accepting as compatible unnamed tag types with the same fields within
   the same translation unit but from 
diff erent types.
+- ``-MG`` now silences the "file not found" errors with ``#embed`` when
+  scanning for dependencies and encountering an unknown file. #GH165632
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------

diff  --git a/clang/lib/Frontend/DependencyFile.cpp 
b/clang/lib/Frontend/DependencyFile.cpp
index 15fa7de35df97..93e012b163878 100644
--- a/clang/lib/Frontend/DependencyFile.cpp
+++ b/clang/lib/Frontend/DependencyFile.cpp
@@ -75,6 +75,17 @@ struct DepCollectorPPCallbacks : public PPCallbacks {
                                     /*IsMissing*/ false);
   }
 
+  bool EmbedFileNotFound(StringRef FileName) override {
+    DepCollector.maybeAddDependency(
+        llvm::sys::path::remove_leading_dotslash(FileName),
+        /*FromModule=*/false,
+        /*IsSystem=*/false,
+        /*IsModuleFile=*/false,
+        /*IsMissing=*/true);
+    // Return true to silence the file not found diagnostic.
+    return true;
+  }
+
   void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,
                           StringRef FileName, bool IsAngled,
                           CharSourceRange FilenameRange,

diff  --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 6a5e5d4bad3a6..891c8ab7f3155 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -4018,7 +4018,7 @@ void Preprocessor::HandleEmbedDirective(SourceLocation 
HashLoc, Token &EmbedTok,
       this->LookupEmbedFile(Filename, isAngled, true, LookupFromFile);
   if (!MaybeFileRef) {
     // could not find file
-    if (Callbacks && Callbacks->EmbedFileNotFound(OriginalFilename)) {
+    if (Callbacks && Callbacks->EmbedFileNotFound(Filename)) {
       return;
     }
     Diag(FilenameTok, diag::err_pp_file_not_found) << Filename;

diff  --git a/clang/test/Driver/mg.c b/clang/test/Driver/mg.c
index 82d8a6084e5e0..b7458a08698d3 100644
--- a/clang/test/Driver/mg.c
+++ b/clang/test/Driver/mg.c
@@ -1,5 +1,7 @@
-// RUN: %clang -M -MG -include nonexistent-preinclude.h %s | FileCheck %s
+// RUN: %clang -M -MG -include nonexistent-preinclude.h -std=c23 %s | 
FileCheck %s
 // CHECK: nonexistent-preinclude.h
 // CHECK: nonexistent-ppinclude.h
+// CHECK: nonexistent-embed
 
 #include "nonexistent-ppinclude.h"
+#embed "nonexistent-embed"


        
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