[clang] fix: compatible C++ empty record with align UB with gcc (PR #72197)

[Erich Keane via cfe-commits]

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@@ -296,10 +296,16 @@ bool CodeGen::isEmptyRecord(ASTContext &Context, QualType T, bool AllowArrays,
     return false;
 
   // If this is a C++ record, check the bases first.
-  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
+  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
     for (const auto &I : CXXRD->bases())
       if (!isEmptyRecord(Context, I.getType(), true, AsIfNoUniqueAddr))
         return false;
+    // C++ object size >= 1 byte, empty struct is 1 byte.
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erichkeane wrote:

This addition makes this not match the comment above, and makes me think that we're doing this wrong.  This ends up applying to only C++ and not C, which seems wrong.  Additionally, I don't think that the assumption of 'greater than 1 byte' is the right way to determine this empty.  Perhaps one of the codegen folks would have a better idea.

https://github.com/llvm/llvm-project/pull/72197