C Macro cheatsheet¶
Predefined Macros¶
Macro |
descriptions |
|---|---|
__FILE__ |
current file name |
__DATE__ |
current compile date in “MMM DD YYYY”” format. |
__TIME__ |
current compile time in “HH:MM:SS” format. |
__LINE__ |
current line number |
__func__ |
current function name |
#include <stdio.h>
int main(int argc, char *argv[])
{
int ret = -1;
printf("__FILE__: %s\n"
"__DATE__: %s\n"
"__TIME__: %s\n"
"__LINE__: %d\n"
"__func__: %s\n",
__FILE__, __DATE__, __TIME__, __LINE__, __func__);
ret = 0;
return ret;
}
output:
$ cc -g -Wall -o test test.c
$ ./test
__FILE__: test.c
__DATE__: Sep 28 2016
__TIME__: 10:01:59
__LINE__: 16
__func__: main
DEBUG switch¶
#include <stdio.h>
int main(int argc, char *argv[])
{
int ret = -1;
#ifdef DEBUG
printf("debug version\n");
#else
printf("release version\n");
#endif
ret = 0;
return ret;
}
output:
$ cc -g -Wall -o test test.c
$ ./test
release version
$ cc -g -Wall -DDEBUG -o test test.c
$ ./test
debug version
ARRAYSIZE¶
#include <stdio.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
/*
* Entry point
*/
int main(int argc, char *argv[])
{
int ret = -1;
char *pszArr[] = {"Hello", "World", NULL};
printf("array size: %lu\n", ARRAY_SIZE(pszArr));
ret = 0;
return ret;
}
output:
$ cc -g -Wall -o test test.c
$ ./test
array size: 3
FOREACH¶
#include <stdio.h>
#define FOREACH(item, arr) \
for (item=arr; *item; item++)
/*
* Entry point
*/
int main(int argc, char *argv[])
{
int ret = -1;
char *pszArr[] = {"Hello", "World", NULL};
char **str = NULL;
FOREACH (str, pszArr) {
printf("%s ", *str);
}
printf("\n");
ret = 0;
return ret;
}
output:
$ cc -g -Wall -o test test.c
$ ./test
Hello World
ALLOC_STRUCT¶
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define ALLOC_STRUCT(s) ((s *) malloc(sizeof(s)))
#define EXPECT_NOT_NULL(i, ...) \
if (i == NULL) { __VA_ARGS__ }
#define EXPECT_ALLOC_SUCCESS(i, fmt, ...) \
EXPECT_NOT_NULL(i, printf(fmt, ##__VA_ARGS__); goto End;)
typedef struct _foo {
int hello;
int world;
} foo;
int main(int argc, char *argv[])
{
int ret = -1;
foo *f = NULL;
f = ALLOC_STRUCT(foo);
EXPECT_ALLOC_SUCCESS(f, "err: %s", strerror(errno));
printf("alloc foo success\n");
ret = 0;
End:
return ret;
}
output:
$ gcc -g -Wall -o test test.c
$ ./test
alloc foo success
lambda¶
#define lambda(return_type, ...) \
__extension__ \
({ \
return_type __fn__ __VA_ARGS__ \
__fn__; \
})
/*
* Entry point
*/
int main(int argc, char *argv[])
{
int ret = -1;
int (*max) (int, int) =
lambda (int, (int x, int y) { return x > y ? x : y; });
printf("lambda: %d\n", max(2,3));
ret = 0;
return ret;
}
output:
$ gcc -g -Wall -o test test.c
$ ./test
lambda: 3
EXPECT_*¶
#include <stdio.h> [19/1840]
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#define EXPECT_TRUE(i, ...) \
if (i != 1) { __VA_ARGS__ }
#define EXPECT_FALSE(i, ...) \
if (i != 0) { __VA_ARGS__ }
#define EXPECT_EQ(i, e, ...) \
if (i != e) { __VA_ARGS__ }
#define EXPECT_NEQ(i, e, ...) \
if (i == e) { __VA_ARGS__ }
#define EXPECT_LT(i, e, ...) \
if (i >= e) { __VA_ARGS__ }
#define EXPECT_LE(i, e, ...) \
if (i > e) { __VA_ARGS__ }
#define EXPECT_GT(i, e, ...) \
if (i <= e) { __VA_ARGS__ }
#define EXPECT_GE(i, e, ...) \
if (i < e) { __VA_ARGS__ }
#define EXPECT_SUCCESS(ret, fmt, ...) \
EXPECT_GT(ret, 0, \
printf(fmt, ##__VA_ARGS__); \
goto End; \
)
/*
* Entry point
*/
int main(int argc, char *argv[])
{
int ret = -1;
EXPECT_TRUE(1);
EXPECT_FALSE(0);
EXPECT_LT(1, 0, printf("check less then fail\n"););
EXPECT_GT(0, 1, printf("check great then fail\n"););
EXPECT_SUCCESS(ret, "ret = %d\n", ret);
ret = 0;
End:
return ret;
}
output:
$ cc -g -Wall -o checkerr checkerr.c
$ ./checkerr
check less then fail
check great then fail
ret = -1
Get struct member GET_FIELD_PTR¶
#include <stdio.h>
#define _GET_FIELD_OFFSET(s, field ) \
((short)(long)(&((s *)NULL)->field))
#define _GET_FIELD_PTR(ps, offset) \
((void *)(((char *)ps) + (offset)))
#define GET_FIELD_PTR(s, ps, field) \
_GET_FIELD_PTR(ps, _GET_FIELD_OFFSET(s, field))
typedef struct _foo {
char name[16];
int age;
int gender;
} foo;
/*
* Entry point
*/
int main(int argc, char *argv[])
{
int ret = -1;
char *name = NULL;
int *age = NULL, *gender = NULL;
foo f = {.name="c", .age=44, .gender=0};
name = GET_FIELD_PTR(foo, &f, name);
age = GET_FIELD_PTR(foo, &f, age);
gender = GET_FIELD_PTR(foo, &f, gender);
printf("name: %s\n"
"age: %d\n"
"gender: %d\n", name, *age, *gender);
ret = 0;
return ret;
}
output:
$ cc -g -Wall -o test test.c
$ ./test
name: c
age: 44
gender: 0
define __attribute__ ((*))¶
#if __GNUC__ >= 3
#undef inline
#define inline inline __attribute__ ((always_inline))
#define __noinline __attribute__ ((noinline))
#define __pure __attribute__ ((pure))
#define __const __attribute__ ((const))
#define __noreturn __attribute__ ((noreturn))
#define __malloc __attribute__ ((malloc))
#define __must_check __attribute__ ((warn_unused_result))
#define __deprecated __attribute__ ((deprecated))
#define __used __attribute__ ((used))
#define __unused __attribute__ ((unused))
#define __packed __attribute__ ((packed))
#define __align(x) __attribute__ ((aligned, (x)))
#define __align_max __attribute__ ((aligned))
#define likely(x) __builtin_expect (!!(x), 1)
#define unlikely(x) __builtin_expect (!!(x), 0)
#else
#undef inline
#define __noinline /* no noinline */
#define __pure /* no pure */
#define __const /* no const */
#define __noreturn /* no noreturn */
#define __malloc /* no malloc */
#define __must_check /* no warn_unused_result */
#define __deprecated /* no deprecated */
#define __used /* no used */
#define __unused /* no unused */
#define __packed /* no packed */
#define __align(x) /* no aligned */
#define __align_max /* no align_max */
#define likely(x) (x)
#define unlikely(x) (x)
#endif
