[PATCH] D148901: [clang][Interp] Fix post-inc/dec operator result

[Timm Bäder via Phabricator via cfe-commits]

tbaeder created this revision.
tbaeder added reviewers: aaron.ballman, taramana, erichkeane, shafik.
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  We pushed the wrong value on the stack, always leaving a 0 behind.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148901

Files:
  clang/lib/AST/Interp/Interp.h
  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
@@ -706,6 +706,23 @@
              // 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
 
Index: clang/lib/AST/Interp/Interp.h
===================================================================
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -437,7 +437,7 @@
   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)) {


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