Added warning on structures/unions that are empty or contain only
bit fields of zero size. Warnings are generated in C++ mode and if
only such type is defined inside extern "C" block.
The patch fixed PR5065.
Differential Revision: http://llvm-reviews.chandlerc.com/D2151
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194653 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index a7b37c5..c0be341 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -12085,8 +12085,21 @@
if (Record->hasAttrs())
CheckAlignasUnderalignment(Record);
- // Check if the structure/union declaration is a language extension.
+ // Check if the structure/union declaration is a type that can have zero
+ // size in C. For C this is a language extension, for C++ it may cause
+ // compatibility problems.
+ bool CheckForZeroSize;
if (!getLangOpts().CPlusPlus) {
+ CheckForZeroSize = true;
+ } else {
+ // For C++ filter out types that cannot be referenced in C code.
+ CXXRecordDecl *CXXRecord = cast<CXXRecordDecl>(Record);
+ CheckForZeroSize =
+ CXXRecord->getLexicalDeclContext()->isExternCContext() &&
+ !CXXRecord->isDependentType() &&
+ CXXRecord->isCLike();
+ }
+ if (CheckForZeroSize) {
bool ZeroSize = true;
bool IsEmpty = true;
unsigned NonBitFields = 0;
@@ -12106,19 +12119,22 @@
}
}
- // Empty structs are an extension in C (C99 6.7.2.1p7), but are allowed in
- // C++.
- if (ZeroSize)
- Diag(RecLoc, diag::warn_zero_size_struct_union_compat) << IsEmpty
- << Record->isUnion() << (NonBitFields > 1);
+ // Empty structs are an extension in C (C99 6.7.2.1p7). They are
+ // allowed in C++, but warn if its declaration is inside
+ // extern "C" block.
+ if (ZeroSize) {
+ Diag(RecLoc, getLangOpts().CPlusPlus ?
+ diag::warn_zero_size_struct_union_in_extern_c :
+ diag::warn_zero_size_struct_union_compat)
+ << IsEmpty << Record->isUnion() << (NonBitFields > 1);
+ }
- // Structs without named members are extension in C (C99 6.7.2.1p7), but
- // are accepted by GCC.
- if (NonBitFields == 0) {
- if (IsEmpty)
- Diag(RecLoc, diag::ext_empty_struct_union) << Record->isUnion();
- else
- Diag(RecLoc, diag::ext_no_named_members_in_struct_union) << Record->isUnion();
+ // Structs without named members are extension in C (C99 6.7.2.1p7),
+ // but are accepted by GCC.
+ if (NonBitFields == 0 && !getLangOpts().CPlusPlus) {
+ Diag(RecLoc, IsEmpty ? diag::ext_empty_struct_union :
+ diag::ext_no_named_members_in_struct_union)
+ << Record->isUnion();
}
}
} else {