[PATCH] D32675: in expression evaluator, treat non-literal types as discarded value expressions if EvalInfo says to continue evaluating them

[Nick Lewycky via Phabricator via cfe-commits]

nlewycky created this revision.

Make the integer overflow evaluator continue into expressions with non-literal types, notably void.

In passing it fixes a crash attempting to codegen:

  struct A { char x; };
  struct B : virtual A {};
  A &a = ((A&)*(B*)0);

which we nearly have a test for except that it casted to void and therefore was ignored instead of being evaluated. The existing test (test/SemaCXX/cstyle-cast.cpp) is sufficient to cover this case now that we don't stop at a void cast.


https://reviews.llvm.org/D32675

Files:
  lib/AST/ExprConstant.cpp
  test/Sema/integer-overflow.c


Index: test/Sema/integer-overflow.c
===================================================================
--- test/Sema/integer-overflow.c
+++ test/Sema/integer-overflow.c
@@ -149,16 +149,16 @@
 
 // expected-warning at +2 {{overflow in expression; result is 536870912 with type 'int'}}
   uint64_t *b;
-  uint64_t b2 = b[4608 * 1024 * 1024] + 1;
+  (void)b[4608 * 1024 * 1024];
 
 // expected-warning at +1 2{{overflow in expression; result is 536870912 with type 'int'}}
-  int j1 = i ? (4608 * 1024 * 1024) : (4608 * 1024 * 1024);
+  (void)(i ? (4608 * 1024 * 1024) : (4608 * 1024 * 1024));
 
 // expected-warning at +1 {{overflow in expression; result is 536870912 with type 'int'}}
-  int j2 = -(4608 * 1024 * 1024);
+  (void)(-(4608 * 1024 * 1024));
 
 // expected-warning at +1 {{overflow in expression; result is 536870912 with type 'int'}}
-  uint64_t j3 = b[4608 * 1024 * 1024];
+  (void)b[4608 * 1024 * 1024];
 
 // expected-warning at +1 2{{overflow in expression; result is 536870912 with type 'int'}}
   return ((4608 * 1024 * 1024) + ((uint64_t)(4608 * 1024 * 1024)));
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -2169,6 +2169,9 @@
   if (!Base->isVirtual())
     return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
 
+  if (!Obj.checkNullPointer(Info, E, CSK_Base))
+    return false;
+
   SubobjectDesignator &D = Obj.Designator;
   if (D.Invalid)
     return false;
@@ -9913,8 +9916,11 @@
   if (E->getType().isNull())
     return false;
 
-  if (!CheckLiteralType(Info, E))
+  if (!CheckLiteralType(Info, E)) {
+    if (Info.noteFailure())
+      EvaluateIgnoredValue(Info, E);
     return false;
+  }
 
   if (!::Evaluate(Result, Info, E))
     return false;


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