[clang] [clang][bytecode] Diagnose unknown reference params pre-C++23 (PR #175013)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

Otherwise, we will ultimately create dummy pointers for them and possibly not diagnose anything.

---
Full diff: https://github.com/llvm/llvm-project/pull/175013.diff


3 Files Affected:

- (modified) clang/lib/AST/ByteCode/Compiler.cpp (+4) 
- (modified) clang/lib/AST/ByteCode/Interp.cpp (+3-2) 
- (modified) clang/test/AST/ByteCode/cxx23.cpp (+17) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index e85ccafc0e53b..cbee7691565a9 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -7076,6 +7076,10 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
 
       return this->emitGetPtrParam(It->second.Offset, E);
     }
+
+    if (!Ctx.getLangOpts().CPlusPlus23 && IsReference)
+      return this->emitInvalidDeclRef(cast<DeclRefExpr>(E),
+                                      /*InitializerFailed=*/false, E);
   }
   // Local variables.
   if (auto It = Locals.find(D); It != Locals.end()) {
diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index 6444025d6fcf8..5394466dd72e3 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -144,9 +144,10 @@ static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
   if (isa<ParmVarDecl>(D)) {
     if (D->getType()->isReferenceType()) {
       if (S.inConstantContext() && S.getLangOpts().CPlusPlus &&
-          !S.getLangOpts().CPlusPlus11)
+          !S.getLangOpts().CPlusPlus11) {
         diagnoseNonConstVariable(S, OpPC, D);
-      return false;
+        return false;
+      }
     }
 
     const SourceInfo &Loc = S.Current->getSource(OpPC);
diff --git a/clang/test/AST/ByteCode/cxx23.cpp b/clang/test/AST/ByteCode/cxx23.cpp
index 4a4ff4b48e8b5..4b87f44d14345 100644
--- a/clang/test/AST/ByteCode/cxx23.cpp
+++ b/clang/test/AST/ByteCode/cxx23.cpp
@@ -520,3 +520,20 @@ namespace InactiveLocalsInConditionalOp {
 
 }
 #endif
+
+namespace UnknownParams {
+  class X {
+  public:
+    constexpr operator bool(){ return true; }
+  };
+  int foo(X x) {
+    static_assert(x);
+    return 1;
+  }
+
+  int foo2(X &x) { // all20-note {{declared here}}
+    static_assert(x); // all20-error {{not an integral constant expression}} \
+                      // all20-note {{function parameter 'x' with unknown value cannot be used in a constant expression}}
+    return 1;
+  }
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/175013