[PATCH] D149828: [clang][Interp] Evaluate Base when discarding a MemberExpr

[Timm Bäder via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG6aac11bad976: [clang][Interp] Evaluate Base when discarding a MemberExpr (authored by tbaeder).

Changed prior to commit:
  https://reviews.llvm.org/D149828?vs=519395&id=545957#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149828/new/

https://reviews.llvm.org/D149828

Files:
  clang/lib/AST/Interp/ByteCodeExprGen.cpp
  clang/test/AST/Interp/literals.cpp


Index: clang/test/AST/Interp/literals.cpp
===================================================================
--- clang/test/AST/Interp/literals.cpp
+++ clang/test/AST/Interp/literals.cpp
@@ -876,7 +876,7 @@
 }
 static_assert(ignoredDecls() == 12, "");
 
-struct A{};
+struct A{ int a; };
 constexpr int ignoredExprs() {
   (void)(1 / 2);
   A a;
@@ -908,6 +908,19 @@
 constexpr int Value = Comma(5);
 static_assert(Value == 8, "");
 
+/// Ignored MemberExprs need to still evaluate the Base
+/// expr.
+constexpr A callme(int &i) {
+  ++i;
+  return A{};
+}
+constexpr int ignoredMemberExpr() {
+  int i = 0;
+  callme(i).a; // ref-warning {{result unused}} \
+               // expected-warning {{result unused}}
+  return i;
+}
+static_assert(ignoredMemberExpr() == 1, "");
 #endif
 
 namespace PredefinedExprs {
Index: clang/lib/AST/Interp/ByteCodeExprGen.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -562,18 +562,18 @@
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitMemberExpr(const MemberExpr *E) {
-  if (DiscardResult)
-    return true;
-
   // 'Base.Member'
   const Expr *Base = E->getBase();
-  const ValueDecl *Member = E->getMemberDecl();
+
+  if (DiscardResult)
+    return this->discard(Base);
 
   if (!this->visit(Base))
     return false;
 
   // Base above gives us a pointer on the stack.
   // TODO: Implement non-FieldDecl members.
+  const ValueDecl *Member = E->getMemberDecl();
   if (const auto *FD = dyn_cast<FieldDecl>(Member)) {
     const RecordDecl *RD = FD->getParent();
     const Record *R = getRecord(RD);


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