[clang] 1732748 - [Analyzer] No longer crash with VLA operands to unary type traits (#151719)

[via cfe-commits]

Author: Aaron Ballman
Date: 2025-08-01T12:31:56-04:00
New Revision: 17327482f045b7119e116320db3e9c12fcf250ae

URL: https://github.com/llvm/llvm-project/commit/17327482f045b7119e116320db3e9c12fcf250ae
DIFF: https://github.com/llvm/llvm-project/commit/17327482f045b7119e116320db3e9c12fcf250ae.diff

LOG: [Analyzer] No longer crash with VLA operands to unary type traits (#151719)

sizeof was handled correctly, but __datasizeof and _Countof were not.

Fixes #151711

Added: 
    clang/test/Analysis/engine/gh151711.cpp

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 20cadbfd00d42..247d784739f4d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -241,6 +241,8 @@ Static Analyzer
 ---------------
 - The Clang Static Analyzer now handles parenthesized initialization.
   (#GH148875)
+- ``__datasizeof`` (C++) and ``_Countof`` (C) no longer cause a failed assertion
+  when given an operand of VLA type. (#GH151711)
 
 New features
 ^^^^^^^^^^^^

diff  --git a/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
index f1a25a750dd0d..4ddf8fd5b4b0f 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp
@@ -868,7 +868,8 @@ VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex,
   QualType T = Ex->getTypeOfArgument();
 
   for (ExplodedNode *N : CheckedSet) {
-    if (Ex->getKind() == UETT_SizeOf) {
+    if (Ex->getKind() == UETT_SizeOf || Ex->getKind() == UETT_DataSizeOf ||
+        Ex->getKind() == UETT_CountOf) {
       if (!T->isIncompleteType() && !T->isConstantSizeType()) {
         assert(T->isVariableArrayType() && "Unknown non-constant-sized type.");
 

diff  --git a/clang/test/Analysis/engine/gh151711.cpp b/clang/test/Analysis/engine/gh151711.cpp
new file mode 100644
index 0000000000000..a9950a7a3b9d0
--- /dev/null
+++ b/clang/test/Analysis/engine/gh151711.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify -x c %s
+
+void clang_analyzer_dump(int);
+
+// Ensure that VLA types are correctly handled by unary type traits in the
+// expression engine. Previously, __datasizeof and _Countof both caused failed
+// assertions.
+void gh151711(int i) {
+  clang_analyzer_dump(sizeof(int[i++]));       // expected-warning {{Unknown}}
+#ifdef __cplusplus
+  // __datasizeof is only available in C++.
+  clang_analyzer_dump(__datasizeof(int[i++])); // expected-warning {{Unknown}}
+#else
+  // _Countof is only available in C.
+  clang_analyzer_dump(_Countof(int[i++]));     // expected-warning {{Unknown}}
+#endif
+}