C bindings: Fix signed comparsion.

mojo/public/c/bindings/lib/type_descriptor.c

Index: mojo/public/c/bindings/lib/type_descriptor.c
diff --git a/mojo/public/c/bindings/lib/type_descriptor.c b/mojo/public/c/bindings/lib/type_descriptor.c
index 2846965b02ee033f267a1463a89ff4fbd5702065..fb9df41ed5c3854e3e4a94c33faa999e7ad8809f 100644
--- a/mojo/public/c/bindings/lib/type_descriptor.c
+++ b/mojo/public/c/bindings/lib/type_descriptor.c
@@ -5,6 +5,7 @@
 #include "mojo/public/c/bindings/lib/type_descriptor.h"
 
 #include <assert.h>
+#include <stddef.h>
 
 #include "mojo/public/c/bindings/array.h"
 #include "mojo/public/c/bindings/interface.h"
@@ -85,7 +86,7 @@ static void encode_pointer(union MojomPointer* pointer, uint32_t max_offset) {
     pointer->offset = 0;
   } else {
     assert((char*)pointer->ptr > (char*)pointer);
-    assert((char*)pointer->ptr - (char*)pointer < max_offset);
+    assert((char*)pointer->ptr - (char*)pointer < (ptrdiff_t)max_offset);

[viettrungluu, 2016/08/02 20:10:29]

Hmmm. So if ptrdiff_t is 32-bit, and max_offset is big, you might have a
problem.

But since you already asserted the pointer->ptr > pointer on the previous line,
you know that the LHS is positive.

So maybe cast all of the LHS to a size_t instead?

[vardhan, 2016/08/02 20:28:30]

Done.

     pointer->offset = (char*)(pointer->ptr) - (char*)pointer;
   }
 }