[clang] [clang][bytecode] Reject strcmp with non-primitive element types (PR #230396)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/230396.diff


2 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+2-1) 
- (modified) clang/test/AST/ByteCode/c.c (+6) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 5f3f59ae242456..4a5c691d390a71 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -325,7 +325,8 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
 
   QualType ElemTy = getElemType(A);
   // Different element types shouldn't happen, but with casts they can.
-  if (!S.getASTContext().hasSameUnqualifiedType(ElemTy, getElemType(B)))
+  if (!S.getASTContext().hasSameUnqualifiedType(ElemTy, getElemType(B)) ||
+      !S.getContext().canClassify(ElemTy))
     return false;
 
   PrimType ElemT = *S.getContext().classify(ElemTy);
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 7dd3f667559ed9..e431691ed190d8 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -486,3 +486,9 @@ Parse sqlite3Prepare_sParse;
 void sqlite3Prepare(void) {
   memset( ((char *)&sqlite3Prepare_sParse) + sizeof(int), 0, sizeof(int));
 }
+
+int strcmp(const char *, const char *);
+const union u {
+  char c[2];
+} str[] = {"", ""};
+const int strcmpFoo = strcmp((const char *)str, (const char *)str); // all-error {{not a compile-time constant}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/230396