[clang][bytecode] Guard strcmp against differing element types

[tbaederr]

This can happen when casts are involved.

Fixes #154006

[llvmbot]

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

Changes

This can happen when casts are involved.

Fixes #154006

---

Full diff: https://github.com/llvm/llvm-project/pull/154777.diff

2 Files Affected:

• (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+6-1)
• (modified) clang/test/AST/ByteCode/c.c (+9)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 2cbebaf7b630e..7516694be8da7 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -205,6 +205,8 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
 
   if (A.isDummy() || B.isDummy())
     return false;
+  if (!A.isBlockPointer() || !B.isBlockPointer())
+    return false;
 
   bool IsWide = ID == Builtin::BIwcscmp || ID == Builtin::BIwcsncmp ||
                 ID == Builtin::BI__builtin_wcscmp ||
@@ -212,7 +214,10 @@ static bool interp__builtin_strcmp(InterpState &S, CodePtr OpPC,
   assert(A.getFieldDesc()->isPrimitiveArray());
   assert(B.getFieldDesc()->isPrimitiveArray());
 
-  assert(getElemType(A).getTypePtr() == getElemType(B).getTypePtr());
+  // Different element types shouldnt' happen, but with casts they can.
+  if (!S.getASTContext().hasSameUnqualifiedType(getElemType(A), getElemType(B)))
+    return false;
+
   PrimType ElemT = *S.getContext().classify(getElemType(A));
 
   auto returnResult = [&](int V) -> bool {
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 654b3da2b7d66..73469d7fd6cc4 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -338,3 +338,12 @@ static void *FooTable[1] = {
     }
 };
 
+int strcmp(const char *, const char *); // all-note {{passing argument to parameter here}}
+#define S "\x01\x02\x03\x04\x05\x06\x07\x08"
+const char _str[] = {S[0], S[1], S[2], S[3], S[4], S[5], S[6], S[7]};
+const unsigned char _str2[] = {S[0], S[1], S[2], S[3], S[4], S[5], S[6], S[7]};
+const int compared = strcmp(_str, (const char *)_str2); // all-error {{initializer element is not a compile-time constant}}
+
+
+const int compared2 = strcmp(strcmp, _str); // all-warning {{incompatible pointer types}} \
+                                            // all-error {{initializer element is not a compile-time constant}}

[shafik]

Isn't this reject b/c of the reinterpret_cast? While the change is about the guard in interp__builtin_strcmp? Am I missing something?

[tbaederr]

The cast causes a CCEDiag but we continue evaluation so it reaches the __builtin_strcmp.