[PATCH] D157252: [clang][ExprConst] Handle 0 type size in builtin_memcpy etc.

[Timm Bäder via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGaaaece65a80f: [clang][ExprConst] Handle 0 type size in builtin_memcpy etc. (authored by tbaeder).

Changed prior to commit:
  https://reviews.llvm.org/D157252?vs=557826&id=557859#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D157252/new/

https://reviews.llvm.org/D157252

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/Sema/builtin-memcpy.c


Index: clang/test/Sema/builtin-memcpy.c
===================================================================
--- /dev/null
+++ clang/test/Sema/builtin-memcpy.c
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 %s -fsyntax-only -verify=c
+// RUN: %clang_cc1 -x c++ %s -fsyntax-only -verify=cxx
+
+// cxx-no-diagnostics
+
+
+/// Zero-sized structs should not crash.
+int b() {
+  struct {      } a[10];
+  __builtin_memcpy(&a[2], a, 2); // c-warning {{buffer has size 0, but size argument is 2}}
+  return 0;
+}
+
+#ifdef __cplusplus
+// FIXME: This is UB and GCC correctly diagnoses it. Clang should do the same.
+constexpr int b2() {
+  struct {      } a[10];
+  __builtin_memcpy(&a[2], a, 2);
+  return 0;
+}
+static_assert(b2() == 0, "");
+#endif
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -9545,6 +9545,8 @@
 
     // Figure out how many T's we're copying.
     uint64_t TSize = Info.Ctx.getTypeSizeInChars(T).getQuantity();
+    if (TSize == 0)
+      return false;
     if (!WChar) {
       uint64_t Remainder;
       llvm::APInt OrigN = N;


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