[analyzer] Relax an assertion in VisitLvalArraySubscriptExpr

The analyzer thinks that ArraySubscriptExpr cannot be an r-value (ever).
However, it can be in some corner cases. Specifically, C forbids expressions
of unqualified void type from being l-values.

Note, the analyzer will keep modeling the subscript expr as an l-value. The
analyzer should be treating void* as a char array
(https://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Pointer-Arith.html).

llvm-svn: 228249

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/test/Analysis/array-struct.c b/clang/test/Analysis/array-struct.c
index c22f9796e58..28e09ad2e88 100644
--- a/clang/test/Analysis/array-struct.c
+++ b/clang/test/Analysis/array-struct.c
@@ -183,3 +183,19 @@ int offset_of_data_array(void)
   return ((char *)&(((struct s*)0)->data_array)) - ((char *)0); // no-warning
 }
 
+int testPointerArithmeticOnVoid(void *bytes) {
+  int p = 0;
+  if (&bytes[0] == &bytes[1])
+    return 6/p; // no-warning
+  return 0;
+}
+
+int testRValueArraySubscriptExpr(void *bytes) {
+  int *p = (int*)&bytes[0];
+  *p = 0;
+  if (*(int*)&bytes[0] == 0)
+    return 0;
+  return 5/(*p); // no-warning
+}
+
+