[PATCH] D119651: [clang] Fix evaluation context type for consteval function calls in instantiations

[Evgeny Shulgin via Phabricator via cfe-commits]

Izaron updated this revision to Diff 409035.
Izaron added a comment.

I've added an assert that will prevent similar bugs. Let's look if we're good with this one?
Here is the list of eval contexts:
https://github.com/llvm/llvm-project/blob/87b218b42b14e392aa0363a413d440b77bf04bd4/clang/include/clang/Sema/Sema.h#L1191-L1239
Should we also check for `PotentiallyEvaluatedIfUsed` or it is too much?
Looks like only two eval contexts from the list may be evaluated in run-time.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119651/new/

https://reviews.llvm.org/D119651

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/lib/Sema/SemaTemplateInstantiateDecl.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 +613,24 @@
 
 } // namespace unevaluated
 
+namespace templated {
+
+consteval int f(int v) {
+  return v;
+}
+
+template <typename T>
+consteval int g(T a) {
+  // Previously this call was rejected due to incorrect evaluation context
+  // type in instantiations. Now we show that this call is OK.
+  int n = f(a);
+  return n;
+}
+
+static_assert(g(100) == 100);
+
+} // namespace templated
+
 namespace PR50779 {
 struct derp {
   int b = 0;
Index: clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -5326,8 +5326,13 @@
     Var->setImplicitlyInline();
 
   if (OldVar->getInit()) {
-    EnterExpressionEvaluationContext Evaluated(
-        *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, Var);
+    ExpressionEvaluationContext Context =
+        ExpressionEvaluationContext::PotentiallyEvaluated;
+    // If current context is constant evaluated, the variable initializer
+    // context is also constant evaluated
+    if (isConstantEvaluated())
+      Context = ExpressionEvaluationContext::ConstantEvaluated;
+    EnterExpressionEvaluationContext Evaluated(*this, Context, Var);
 
     // Instantiate the initializer.
     ExprResult Init;
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -16637,6 +16637,11 @@
     ExpressionEvaluationContextRecord::ExpressionKind ExprContext) {
   ExprEvalContexts.emplace_back(NewContext, ExprCleanupObjects.size(), Cleanup,
                                 LambdaContextDecl, ExprContext);
+  assert(
+      !(ExprEvalContexts.back().Context ==
+            ExpressionEvaluationContext::PotentiallyEvaluated &&
+        ExprEvalContexts[ExprEvalContexts.size() - 2].isConstantEvaluated()) &&
+      "Can't have an evaluated context within an unevaluated context!");
 
   // Discarded statements and immediate contexts nested in other
   // discarded statements or immediate context are themselves


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