[clang] [Clang] Static member initializers are not immediate escalating context. (PR #66021)

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llvmbot wrote:

@llvm/pr-subscribers-clang

<details>
<summary>Changes</summary>

Per CWG2760, default members initializers should be consider part the body of constructors, which mean they are evaluated in an immediate escalating context.

However, this does not apply to static members.

This patch produces some extraneous diagnostics, unfortunately we do not have a good way to report an error back to the initializer and this is a pre existing issue

Fixes #65985
--
Full diff: https://github.com/llvm/llvm-project/pull/66021.diff

3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+4) 
- (modified) clang/lib/Parse/ParseDeclCXX.cpp (+10-2) 
- (modified) clang/test/SemaCXX/cxx2b-consteval-propagate.cpp (+23) 


<pre>
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index d3757c833ef83a2..8bc66ee44e3d289 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -161,6 +161,10 @@ Bug Fixes to C++ Support
   requires-expression. This fixes:
   (`#64138 <https://github.com/llvm/llvm-project/issues/64138>_`).
 
+- Fix a crash when calling a non-constant immediate function
+  in the initializer of a static data member.
+  (`#65985 <https://github.com/llvm/llvm-project/issues/65985>_`).
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 42f268b0911b783..c2a2a561a3f0700 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -3229,13 +3229,21 @@ ExprResult Parser::ParseCXXMemberInitializer(Decl *D, bool IsFunction,
   assert(Tok.isOneOf(tok::equal, tok::l_brace) &&
          "Data member initializer not starting with '=' or '{'");
 
+  bool IsFieldInitialization = isa_and_present<FieldDecl>(D);
+
   EnterExpressionEvaluationContext Context(
       Actions,
-      isa_and_present<FieldDecl>(D)
+      IsFieldInitialization
           ? Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed
           : Sema::ExpressionEvaluationContext::PotentiallyEvaluated,
       D);
-  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext = true;
+
+  // CWG2760
+  // Default member initializers used to initialize a base or member subobject
+  // [...] are considered to be part of the function body
+  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+      IsFieldInitialization;
+
   if (TryConsumeToken(tok::equal, EqualLoc)) {
     if (Tok.is(tok::kw_delete)) {
       // In principle, an initializer of '= delete p;' is legal, but it will
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
index c5eb7f139327505..f967ce6554d777c 100644
--- a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -330,3 +330,26 @@ struct S {
 S s(0); // expected-note {{in the default initializer of 'j'}}
 
 }
+
+namespace GH65985 {
+
+int consteval operator""_foo(unsigned long long V) {
+    return 0;
+}
+int consteval operator""_bar(unsigned long long V); // expected-note 3{{here}}
+
+struct C {
+    static const int a = 1_foo;
+    static constexpr int b = 1_foo;
+    static const int c = 1_bar; // expected-error {{call to consteval function 'GH65985::operator""_bar' is not a constant expression}} \
+                                // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}} \
+                                // expected-error {{in-class initializer for static data member is not a constant expression}}
+
+    // FIXME: remove duplicate diagnostics
+    static constexpr int d = 1_bar; // expected-error {{call to consteval function 'GH65985::operator""_bar' is not a constant expression}} \
+                                    // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}} \
+                                    // expected-error {{constexpr variable 'd' must be initialized by a constant expression}}  \
+                                    // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}}
+};
+
+}
</pre>

</details>

https://github.com/llvm/llvm-project/pull/66021