[clang] c3a0eb4 - [Modules] Don't merge attributes for namespace redeclarations. (#214361)

[via cfe-commits]

Author: Volodymyr Sapsai
Date: 2026-08-05T20:55:35-07:00
New Revision: c3a0eb4b8f4f4b5c4b705c04bc3f16e4985ddbdf

URL: https://github.com/llvm/llvm-project/commit/c3a0eb4b8f4f4b5c4b705c04bc3f16e4985ddbdf
DIFF: https://github.com/llvm/llvm-project/commit/c3a0eb4b8f4f4b5c4b705c04bc3f16e4985ddbdf.diff

LOG: [Modules] Don't merge attributes for namespace redeclarations. (#214361)

Follow-up to #208348 which aimed to handle decl attributes on
deserialization the same way as during parsing. Turned out during
parsing we don't merge attributes for namespace redeclarations.

Added: 
    

Modified: 
    clang/lib/Serialization/ASTReaderDecl.cpp
    clang/test/Modules/decl-attr-merge2.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 05ace69a4d999..0ad7cc47f858c 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -3910,7 +3910,7 @@ void ASTDeclReader::attachPreviousDecl(ASTReader &Reader, Decl *D,
 
   if (PreviousNonLocal) {
     if (Sema *S = Reader.getSema()) {
-      if (auto *ND = dyn_cast<NamedDecl>(D))
+      if (auto *ND = dyn_cast<NamedDecl>(D); ND && !isa<NamespaceDecl>(ND))
         S->mergeDeclAttributes(ND, PreviousNonLocal);
     }
   }

diff  --git a/clang/test/Modules/decl-attr-merge2.c b/clang/test/Modules/decl-attr-merge2.c
index fc84b9df70171..6c23fb08f0c9a 100644
--- a/clang/test/Modules/decl-attr-merge2.c
+++ b/clang/test/Modules/decl-attr-merge2.c
@@ -2,7 +2,7 @@
 // RUN: split-file %s %t
 // RUN: %clang_cc1 -fmodules -fimplicit-module-maps \
 // RUN:   -fmodules-cache-path=%t/mcache -triple arm64-apple-macosx10.7.0 \
-// RUN:   -I%t/headers -fsyntax-only %t/test.c -verify
+// RUN:   -I%t/headers -fsyntax-only %t/test.cpp -verify
 
 // Check more cases of attribute merging across multiple modules.
 
@@ -17,11 +17,25 @@ module Second {
 void additiveAttr(void) __attribute__((availability(macos,unavailable)));
 void exclusiveAttr(void) __attribute__((hot));
 
+namespace N {
+inline namespace with_tag __attribute__((__abi_tag__("a"))) {
+  struct First {};
+}
+inline namespace with_tag {
+}
+}
+
 //--- headers/second.h
 void additiveAttr(void) __attribute__((availability(ios,introduced=4.0)));
 void exclusiveAttr(void) __attribute__((cold));
 
-//--- test.c
+namespace N {
+inline namespace with_tag {
+  struct Second {};
+}
+}
+
+//--- test.cpp
 #include <first.h>
 #include <second.h>
 
@@ -35,4 +49,6 @@ void test(void) {
   exclusiveAttr();
   // expected-error at second.h:* {{'cold' and 'hot' attributes are not compatible}}
   // expected-note at first.h:* {{conflicting attribute is here}}
+
+  N::Second second;
 }