[clang] 977d8a4 - [clang][Sema] Fixed Compound Literal is not Constant Expression (#143852)

[via cfe-commits]

Author: Vincent
Date: 2025-06-17T09:20:41-04:00
New Revision: 977d8a4bcd83797217433709201922b9deb97ae2

URL: https://github.com/llvm/llvm-project/commit/977d8a4bcd83797217433709201922b9deb97ae2
DIFF: https://github.com/llvm/llvm-project/commit/977d8a4bcd83797217433709201922b9deb97ae2.diff

LOG: [clang][Sema] Fixed Compound Literal is not Constant Expression (#143852)

Added a check for a compound literal hiding inside a function.

fixes #87867

Added: 
    clang/test/Sema/gh87867.c

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/include/clang/Sema/Scope.h
    clang/lib/Sema/SemaExpr.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 03641f5d0ea0d..6f28dbd03ca2a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -692,6 +692,8 @@ Bug Fixes in This Version
   ``#include`` directive. (#GH138094)
 - Fixed a crash during constant evaluation involving invalid lambda captures
   (#GH138832)
+- Fixed compound literal is not constant expression inside initializer list
+  (#GH87867)
 - Fixed a crash when instantiating an invalid dependent friend template specialization.
   (#GH139052)
 - Fixed a crash with an invalid member function parameter list with a default

diff  --git a/clang/include/clang/Sema/Scope.h b/clang/include/clang/Sema/Scope.h
index ad12a3d73413b..07b9e1bc10f5a 100644
--- a/clang/include/clang/Sema/Scope.h
+++ b/clang/include/clang/Sema/Scope.h
@@ -427,6 +427,17 @@ class Scope {
     return false;
   }
 
+  /// isInObjcMethodScope - Return true if this scope is, or is contained, in an
+  /// C function body.
+  bool isInCFunctionScope() const {
+    for (const Scope *S = this; S; S = S->getParent()) {
+      if (S->isFunctionScope())
+        return true;
+    }
+
+    return false;
+  }
+
   /// isInObjcMethodScope - Return true if this scope is, or is contained in, an
   /// Objective-C method body.  Note that this method is not constant time.
   bool isInObjcMethodScope() const {

diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 413eff4aa294a..ebc43157d4c2b 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -7176,6 +7176,7 @@ Sema::BuildCompoundLiteralExpr(SourceLocation LParenLoc, TypeSourceInfo *TInfo,
   //   void func(char *para[(int [1]){ 0 }[0]);
   const Scope *S = getCurScope();
   bool IsFileScope = !CurContext->isFunctionOrMethod() &&
+                     !S->isInCFunctionScope() &&
                      (!S || !S->isFunctionPrototypeScope());
 
   // In C, compound literals are l-values for some reason.

diff  --git a/clang/test/Sema/gh87867.c b/clang/test/Sema/gh87867.c
new file mode 100644
index 0000000000000..0568c734424ca
--- /dev/null
+++ b/clang/test/Sema/gh87867.c
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c23 %s
+
+// Compound literal doesn't need a constant expression inside a initializer-list if it is already inside a function 
+// see: https://github.com/llvm/llvm-project/issues/87867
+int foo(int *a, int b) {
+    return 0;
+}
+
+int x;
+struct{int t;} a = (struct {
+    typeof(foo(&(struct { int t; }){.t = x}.t, 0)) t; // expected-error {{initializer element is not a compile-time constant}}
+}){0};
+
+void inside_a_func(){
+    int x;
+    (void)(struct {
+        typeof(foo(&(struct { int t; }){.t = x}.t, 0)) t;
+    }){0};
+}
+
+// see: https://github.com/llvm/llvm-project/issues/143613
+#define bitcast(type, value) \
+    (((union{ typeof(value) src; type dst; }){ (value) }).dst)
+
+double placeholder = 10.0;
+double bar = bitcast(double, placeholder);  // expected-error {{initializer element is not a compile-time constant}}
+
+int main(void)
+{
+    int foo = 4;
+    foo = bitcast(int, bitcast(double, foo));
+    return 0;
+}