Merge pull request #157 from goblint/builtin_types_compatible

Ignore top level qualifiers in `__builtin_types_compatible_p`

Author: karoliineh

src/frontc/cabs2cil.ml

@@ -4658,7 +4658,8 @@ and doExp (asconst: bool)   (* This expression is used as a constant *)
                         prechunk := (fun _ -> empty);
                         piscall := false;
                         let compatible =
-                          try ignore(combineTypes CombineOther t1 t2); true
+                          (* This built-in function ignores top level qualifiers (e.g., const, volatile). *)
+                          try ignore(combineTypes CombineOther (removeOuterQualifierAttributes t1) (removeOuterQualifierAttributes t2)); true
                           with Failure _ -> false
                         in
                         if compatible then

test/small1/builtin6.c

@@ -0,0 +1,10 @@
+
+// Extracted from the git repository.
+// CIL used to crash with "Error: Length of array is negative".
+
+int main() {
+    const int *a;
+    int *ret;
+    sizeof(*(ret)) + (sizeof(char [1 - 2*!(__builtin_types_compatible_p(__typeof__(*((ret))), __typeof__(*((a)))))]) - 1);
+    return 0;
+}

test/testcil.pl

@@ -548,6 +548,7 @@ sub addToGroup {
 addTest("testrungcc/builtin_object_size _GNUCC=1 OPTIMIZE=1");
 addTest("testrun/builtin4 ");
 addTest("test/builtin5 ");
+addTest("test/builtin6 ");
 addTest("test/sync-1 _GNUCC=1");
 addTest("test/sync-2 _GNUCC=1");
 addTest("test/sync-3 _GNUCC=1");