[PATCH] D132918: [clang] Fix a crash in constant evaluation

[Kadir Cetinkaya via Phabricator via cfe-commits]

kadircet updated this revision to Diff 457566.
kadircet added a comment.

Add reproducer.

I think the issue is about keeping constexpr functions valid even when their
bodies contain invalid decls under certain instantiations, which I believe is
the right behaviour. As the function body might be invalid for a certain
instantiation at constexpr time, but might be valid for others (or even for the
same instantiation later on in the TU).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132918/new/

https://reviews.llvm.org/D132918

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/SemaCXX/constexpr-value-init.cpp


Index: clang/test/SemaCXX/constexpr-value-init.cpp
===================================================================
--- clang/test/SemaCXX/constexpr-value-init.cpp
+++ clang/test/SemaCXX/constexpr-value-init.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -Wno-uninitialized -std=c++11 -fsyntax-only -verify
+// RUN: %clang_cc1 %s -Wno-uninitialized -std=c++17 -fsyntax-only -verify
 
 struct A {
   constexpr A() : a(b + 1), b(a + 1) {} // expected-note 5{{outside its lifetime}}
@@ -46,3 +46,17 @@
 static_assert(e2.a[0].b == 2, "");
 static_assert(e2.a[1].a == 1, "");
 static_assert(e2.a[1].b == 2, "");
+
+namespace InvalidDeclInsideConstExpr {
+template <int a> struct i; // expected-note {{template is declared here}}
+template <> struct i<0> {};
+
+template <int x> constexpr auto c() {
+  // i<x> is valid, but it might be incomplete. g would be invalid in that case.
+  i<x> g; // expected-error {{implicit instantiation of undefined template 'InvalidDeclInsideConstExpr::i<1>'}}
+  return 0;
+}
+
+auto y = c<1>(); // expected-note {{in instantiation of function template specialization 'InvalidDeclInsideConstExpr::c<1>' requested here}}
+auto x = c<0>(); // this is valid.
+}
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -4844,6 +4844,8 @@
 }
 
 static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
+  if (VD->isInvalidDecl())
+    return false;
   // We don't need to evaluate the initializer for a static local.
   if (!VD->hasLocalStorage())
     return true;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D132918.457566.patch
Type: text/x-patch
Size: 1620 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220902/1d699bea/attachment.bin>