[PATCH] D119375: [Clang][Sema] Do not evaluate value-dependent immediate invocations

[Evgeny Shulgin via Phabricator via cfe-commits]

Izaron created this revision.
Izaron added reviewers: aaron.ballman, cor3ntin.
Izaron requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Value-dependent ConstantExprs are not meant to be evaluated.
There is an assert in Expr::EvaluateAsConstantExpr that ensures this condition.
But before this patch the method was called without prior check.

Fixes https://github.com/llvm/llvm-project/issues/52768


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119375

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/cxx2a-consteval.cpp


Index: clang/test/SemaCXX/cxx2a-consteval.cpp
===================================================================
--- clang/test/SemaCXX/cxx2a-consteval.cpp
+++ clang/test/SemaCXX/cxx2a-consteval.cpp
@@ -613,6 +613,26 @@
 
 } // namespace unevaluated
 
+namespace value_dependent {
+
+consteval int foo(int x) {
+  return x;
+}
+
+template <int X> constexpr int bar() {
+  return foo(X);
+}
+
+template <typename T> constexpr int baz() {
+  constexpr int t = sizeof(T);
+  return foo(t);
+}
+
+static_assert(bar<15>() == 15);
+static_assert(baz<int>() == sizeof(int));
+
+} // namespace value_dependent
+
 namespace PR50779 {
 struct derp {
   int b = 0;
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -16728,7 +16728,10 @@
       ConstantExpr::getStorageKind(Decl->getReturnType().getTypePtr(),
                                    getASTContext()),
       /*IsImmediateInvocation*/ true);
-  ExprEvalContexts.back().ImmediateInvocationCandidates.emplace_back(Res, 0);
+  /// Value-dependent constant expression are not meant to be calculated.
+  /// Each template instantiation will calculate its own value later.
+  if (!Res->isValueDependent())
+    ExprEvalContexts.back().ImmediateInvocationCandidates.emplace_back(Res, 0);
   return Res;
 }
 


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