release/21.x: [clang][modules] Fix crash in enum visibility lookup for C++20 header units (#166272) #166701
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… units (llvm#166272) Fixes llvm#165445. Fixes a crash when `ASTWriter::GenerateNameLookupTable` processes enum constants from C++20 header units. The special handling for enum constants, introduced in fccc6ee, doesn't account for declarations whose owning module is a C++20 header unit. It calls `isNamedModule()` on the result of `getTopLevelOwningNamedModule()`, which returns null for header units, causing a null pointer dereference. (cherry picked from commit bc08e69)
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Author
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@ChuanqiXu9 What do you think about merging this PR to the release branch? |
llvmbot
added
clang
Member
Author
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@llvm/pr-subscribers-clang-modules Author: None (llvmbot) ChangesBackport bc08e69 Requested by: @ChuanqiXu9 Full diff: https://github.com/llvm/llvm-project/pull/166701.diff 2 Files Affected:
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 1a20fc9595dce..3caf9ebb32185 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4340,8 +4340,7 @@ class ASTDeclContextNameLookupTrait
// parent of parent. We DON'T remove the enum constant from its parent. So
// we don't need to care about merging problems here.
if (auto *ECD = dyn_cast<EnumConstantDecl>(D);
- ECD && DC.isFileContext() && ECD->getOwningModule() &&
- ECD->getTopLevelOwningNamedModule()->isNamedModule()) {
+ ECD && DC.isFileContext() && ECD->getTopLevelOwningNamedModule()) {
if (llvm::all_of(
DC.noload_lookup(
cast<EnumDecl>(ECD->getDeclContext())->getDeclName()),
diff --git a/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm b/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm
new file mode 100644
index 0000000000000..90c57796dcf7e
--- /dev/null
+++ b/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm
@@ -0,0 +1,46 @@
+// Fixes #165445
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -x c++-user-header %t/header.h \
+// RUN: -emit-header-unit -o %t/header.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.cppm -fmodule-file=%t/header.pcm \
+// RUN: -emit-module-interface -o %t/A.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/B.cppm -fmodule-file=%t/header.pcm \
+// RUN: -emit-module-interface -o %t/B.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/use.cpp \
+// RUN: -fmodule-file=A=%t/A.pcm -fmodule-file=B=%t/B.pcm \
+// RUN: -fmodule-file=%t/header.pcm \
+// RUN: -verify -fsyntax-only
+
+//--- enum.h
+enum E { Value };
+
+//--- header.h
+#include "enum.h"
+
+//--- A.cppm
+module;
+#include "enum.h"
+export module A;
+
+auto e = Value;
+
+//--- B.cppm
+export module B;
+import "header.h";
+
+auto e = Value;
+
+//--- use.cpp
+// expected-no-diagnostics
+import A;
+import B;
+#include "enum.h"
+
+auto e = Value;
|
Member
Author
|
@llvm/pr-subscribers-clang Author: None (llvmbot) ChangesBackport bc08e69 Requested by: @ChuanqiXu9 Full diff: https://github.com/llvm/llvm-project/pull/166701.diff 2 Files Affected:
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 1a20fc9595dce..3caf9ebb32185 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4340,8 +4340,7 @@ class ASTDeclContextNameLookupTrait
// parent of parent. We DON'T remove the enum constant from its parent. So
// we don't need to care about merging problems here.
if (auto *ECD = dyn_cast<EnumConstantDecl>(D);
- ECD && DC.isFileContext() && ECD->getOwningModule() &&
- ECD->getTopLevelOwningNamedModule()->isNamedModule()) {
+ ECD && DC.isFileContext() && ECD->getTopLevelOwningNamedModule()) {
if (llvm::all_of(
DC.noload_lookup(
cast<EnumDecl>(ECD->getDeclContext())->getDeclName()),
diff --git a/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm b/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm
new file mode 100644
index 0000000000000..90c57796dcf7e
--- /dev/null
+++ b/clang/test/Modules/crash-enum-visibility-with-header-unit.cppm
@@ -0,0 +1,46 @@
+// Fixes #165445
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -x c++-user-header %t/header.h \
+// RUN: -emit-header-unit -o %t/header.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.cppm -fmodule-file=%t/header.pcm \
+// RUN: -emit-module-interface -o %t/A.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/B.cppm -fmodule-file=%t/header.pcm \
+// RUN: -emit-module-interface -o %t/B.pcm
+//
+// RUN: %clang_cc1 -std=c++20 %t/use.cpp \
+// RUN: -fmodule-file=A=%t/A.pcm -fmodule-file=B=%t/B.pcm \
+// RUN: -fmodule-file=%t/header.pcm \
+// RUN: -verify -fsyntax-only
+
+//--- enum.h
+enum E { Value };
+
+//--- header.h
+#include "enum.h"
+
+//--- A.cppm
+module;
+#include "enum.h"
+export module A;
+
+auto e = Value;
+
+//--- B.cppm
+export module B;
+import "header.h";
+
+auto e = Value;
+
+//--- use.cpp
+// expected-no-diagnostics
+import A;
+import B;
+#include "enum.h"
+
+auto e = Value;
|
Member
This is a simple fix. I think there is no risks. |
Collaborator
Could you approve the port request as a formality if it is okay with you? |
ChuanqiXu9
approved these changes
Nov 7, 2025
Member
Done |
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Backport bc08e69
Requested by: @ChuanqiXu9