[liba] Define ssize_t and offsetof

Change-Id: Icbf546cd09f4e3c3e849f830bb3c60ffa3c13b6c

liba/include/stddef.h

@@ -3,10 +3,9 @@
 
 #define NULL 0
 
-/* C99 says that size_t is an unsigned integer type of at least 16 bit.
- * Moreover, size_t is the return type of the "sizeof" operator, which is
- * defined by the compiler. That's why both GCC and clang define a __SIZE_TYPE__
- * macro to let the libc header know about the type used by the compiler. */
-typedef __SIZE_TYPE__ size_t;
+typedef int ssize_t;
+typedef unsigned int size_t;
+
+#define offsetof(st, m) __builtin_offsetof(st, m)
 
 #endif

liba/test/helpers.h

@@ -0,0 +1,7 @@
+#ifndef LIBA_TEST_HELPERS_H
+#define LIBA_TEST_HELPERS_H
+
+#define assert_signed(type) assert((type)-1 < 0)
+#define assert_unsigned(type) assert((type)-1 >= 0)
+
+#endif

liba/test/stddef.c

@@ -0,0 +1,13 @@
+#include <quiz.h>
+#include <stddef.h>
+#include <assert.h>
+#include "helpers.h"
+
+QUIZ_CASE(liba_stddef) {
+  assert(NULL == 0);
+
+  assert_unsigned(size_t);
+  assert(sizeof(size_t) == __SIZEOF_SIZE_T__);
+  assert_signed(ssize_t);
+  assert(sizeof(ssize_t) == __SIZEOF_SIZE_T__);
+}

liba/test/stdint.c

@@ -1,6 +1,7 @@
 #include <quiz.h>
 #include <stdint.h>
 #include <assert.h>
+#include "helpers.h"
 
 QUIZ_CASE(liba_stdint_size) {
   assert(sizeof(uint8_t) == 1);
@@ -14,9 +15,6 @@ QUIZ_CASE(liba_stdint_size) {
   assert(sizeof(int64_t) == 8);
 }
 
-#define assert_signed(type) assert((type)-1 < 0)
-#define assert_unsigned(type) assert((type)-1 >= 0)
-
 QUIZ_CASE(liba_stdint_signedness) {
   assert_signed(int8_t);
   assert_signed(int16_t);