[clang] c2b69b1 - [clang][bytecode] Do a full CheckLoad in builtin_memcmp() (#181337)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-02-13T11:06:40+01:00
New Revision: c2b69b1a173704e246f7501f8e87268ff6afcd01

URL: https://github.com/llvm/llvm-project/commit/c2b69b1a173704e246f7501f8e87268ff6afcd01
DIFF: https://github.com/llvm/llvm-project/commit/c2b69b1a173704e246f7501f8e87268ff6afcd01.diff

LOG: [clang][bytecode] Do a full CheckLoad in builtin_memcmp() (#181337)

This handles unknown size arrays as well and prints the expected
diagnostics.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/InterpBuiltin.cpp
    clang/test/AST/ByteCode/builtin-functions.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index fe704a8e27b99..ac0e854733397 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1990,11 +1990,7 @@ static bool interp__builtin_memcmp(InterpState &S, CodePtr OpPC,
     return false;
   }
 
-  if (PtrA.isDummy() || PtrB.isDummy())
-    return false;
-
-  if (!CheckRange(S, OpPC, PtrA, AK_Read) ||
-      !CheckRange(S, OpPC, PtrB, AK_Read))
+  if (!CheckLoad(S, OpPC, PtrA, AK_Read) || !CheckLoad(S, OpPC, PtrB, AK_Read))
     return false;
 
   // Now, read both pointers to a buffer and compare those.

diff  --git a/clang/test/AST/ByteCode/builtin-functions.cpp b/clang/test/AST/ByteCode/builtin-functions.cpp
index a0e8d61163eb0..6c49d015c1184 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1583,6 +1583,10 @@ namespace Memcmp {
   static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 6) != 0);
   static_assert(__builtin_bcmp("abab\0banana", "abab\0canada", 5) == 0);
 
+  constexpr char abc[] = /* missing */; // both-error {{expected expression}} \
+                                        // both-note {{declared here}}
+  static_assert(__builtin_bcmp(abc, abc, 2) == 0); // both-error {{not an integral constant expression}} \
+                                                   // both-note {{initializer of 'abc' is unknown}}
 
   static_assert(__builtin_wmemcmp(L"abaa", L"abba", 3) == -1);
   static_assert(__builtin_wmemcmp(L"abaa", L"abba", 2) == 0);