Implement custom assert macro

Summary: assert.h assertion gets stripped from builds. I don't want these assertions to be stripped so implement a custom assert macro. This also allows the assertion to be documented with a message.

Reviewed By: javache

Differential Revision: D3648805

fbshipit-source-id: a6bf1bb55e1e0ee37284647ab76d66f3956a66c0

CSSLayout/CSSMacros.h

@@ -16,3 +16,17 @@
 # define CSS_EXTERN_C_BEGIN
 # define CSS_EXTERN_C_END
 #endif
+
+#ifndef FB_ASSERTIONS_ENABLED
+#define FB_ASSERTIONS_ENABLED 1
+#endif
+
+#if !(FB_ASSERTIONS_ENABLED)
+#define abort()
+#endif
+
+#define CSS_ASSERT(X, message) \
+if (!(X)) { \
+  fprintf(stderr, "%s\n", message); \
+  abort(); \
+}