[clang][Interp] Fix post-inc/dec operator result

We pushed the wrong value on the stack, always leaving a 0 behind. Differential Revision: https://reviews.llvm.org/D148901
llvm · Apr 26, 2023 · 3185e47 · 3185e47
1 parent 4343699
commit 3185e47
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/clang/lib/AST/Interp/Interp.h b/clang/lib/AST/Interp/Interp.h
@@ -436,7 +436,7 @@ bool IncDecHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   T Result;
 
   if constexpr (DoPush == PushVal::Yes)
-    S.Stk.push<T>(Result);
+    S.Stk.push<T>(Value);
 
   if constexpr (Op == IncDecOp::Inc) {
     if (!T::increment(Value, &Result)) {

diff --git a/clang/test/AST/Interp/literals.cpp b/clang/test/AST/Interp/literals.cpp
@@ -719,6 +719,23 @@ namespace IncDec {
              // ref-note {{cannot refer to element -1 of array of 3 elements}}
     return *p;
   }
+
+  /// This used to leave a 0 on the stack instead of the previous
+  /// value of a.
+  constexpr int bug1Inc() {
+    int a = 3;
+    int b = a++;
+    return b;
+  }
+  static_assert(bug1Inc() == 3);
+
+  constexpr int bug1Dec() {
+    int a = 3;
+    int b = a--;
+    return b;
+  }
+  static_assert(bug1Dec() == 3);
+
 };
 #endif