[cfe-commits] r143674 - in /cfe/trunk: lib/AST/ExprConstant.cpp test/Sema/const-eval.c

[Richard Smith]

Author: rsmith
Date: Thu Nov  3 20:10:57 2011
New Revision: 143674

URL: http://llvm.org/viewvc/llvm-project?rev=143674&view=rev
Log:
Constant expression evaluation: although we don't know whether a literal will
be at the same address as another object, we do know it won't alias a null
pointer.

Modified:
    cfe/trunk/lib/AST/ExprConstant.cpp
    cfe/trunk/test/Sema/const-eval.c

Modified: cfe/trunk/lib/AST/ExprConstant.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=143674&r1=143673&r2=143674&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ExprConstant.cpp (original)
+++ cfe/trunk/lib/AST/ExprConstant.cpp Thu Nov  3 20:10:57 2011
@@ -1970,8 +1970,10 @@
           return false;
         // It's implementation-defined whether distinct literals will have
         // distinct addresses. In clang, we do not guarantee the addresses are
-        // distinct.
-        if (IsLiteralLValue(LHSValue) || IsLiteralLValue(RHSValue))
+        // distinct. However, we do know that the address of a literal will be
+        // non-null.
+        if ((IsLiteralLValue(LHSValue) || IsLiteralLValue(RHSValue)) &&
+            LHSValue.Base && RHSValue.Base)
           return false;
         // We can't tell whether weak symbols will end up pointing to the same
         // object.

Modified: cfe/trunk/test/Sema/const-eval.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/const-eval.c?rev=143674&r1=143673&r2=143674&view=diff
==============================================================================
--- cfe/trunk/test/Sema/const-eval.c (original)
+++ cfe/trunk/test/Sema/const-eval.c Thu Nov  3 20:10:57 2011
@@ -99,3 +99,6 @@
 extern const int weak_int __attribute__((weak));
 const int weak_int = 42;
 int weak_int_test = weak_int; // expected-error {{not a compile-time constant}}
+
+int literalVsNull1 = "foo" == 0;
+int literalVsNull2 = 0 == "foo";