C __变量类型和printf
如果我使用C __变量类型和printf,c,gcc,printf,C,Gcc,Printf,如果我使用\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu 我的意思是,例如: #define max(a,b) \ ({ typeof (a) _a = (a); \ typeof (b) _b = (b); \ DEBUG(( "%" __PRI_TYPE_PREFIX(a) > "%" __PRI
\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
我的意思是,例如:
#define max(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
DEBUG(( "%" __PRI_TYPE_PREFIX(a) > "%" __PRI_TYPE_PREFIX(b) "?", _a, _b)) \ <-- hypothetical
_a > _b ? _a : _b; })
定义最大值(a,b)\
({typeof(a)_a=(a)\
类型(b)_b=(b)\
调试(“%”类型前缀(a)>“%”类型前缀(b)“?”,\U a,\U b))\\U b?\U a:\U b;})
可能吗?您可以使用C11的
\u Generic
功能来执行此操作,例如
#define printf_dec_format(x) _Generic((x), \
char: "%c", \
signed char: "%hhd", \
unsigned char: "%hhu", \
signed short: "%hd", \
unsigned short: "%hu", \
signed int: "%d", \
unsigned int: "%u", \
long int: "%ld", \
unsigned long int: "%lu", \
long long int: "%lld", \
unsigned long long int: "%llu", \
float: "%f", \
double: "%f", \
long double: "%Lf", \
char *: "%s", \
void *: "%p")
#define print(x) printf(printf_dec_format(x), x)
(示例取自:)#包括
#定义FMT(_pre_uuuuuu,x,_post_uuuuu)_Generic((x)\
字符:_pre_uuu“%c”\u post\uuu\
int:_pre_uuuuuuuuuuuuud”\u post\uuuu\
长:_pre_uuu“%ld”\u post_uuu)
int main()
{
int x=42;
长y=432144312432321;
printf(FMT(“foo:”,x,“\n”),x);
printf(FMT(“条:”,y,“\n”),y);
返回0;
}
前期和后期的东西有点难看,但我还没有找到更好的方法。我们不能依赖C预处理器中的字符串连接,因为编译器对
\u Generic
进行计算太晚了。例如,使用C11\u Generic
(必须完成才能进行完整检查):
或者使用\u内置类型\u兼容\u p
gcc扩展:
#define max(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
if (__builtin_types_compatible_p(typeof(int), _a) && __builtin_types_compatible_p(typeof(int), _a)) DEBUG_INT(_a, _b); \
else if (__builtin_types_compatible_p(typeof(double), _a) && __builtin_types_compatible_p(typeof(double), _a)) DEBUG_DOUBLE(_a, _b); \
else FAIL(_a, _b);
_a > _b ? _a : _b; })
从博客链接中,我可以看到只有
clang
支持此功能!:(,到目前为止,我使用的是gcc-4.6.3
@vyom gcc还支持\u Generic
,但您需要更新的版本。
#define DEBUG_INT(a, b) DEBUG("%d %d?", (a), (b))
#define DEBUG_DOUBLE(a, b) DEBUG("%f %f?", (a), (b))
#define FAIL(a, b) assert(0)
#define max(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
_Generic((_a), int: DEBUG_INT, double: DEBUG_DOUBLE, default: FAIL))(_a, _b); \
_a > _b ? _a : _b; })
#define max(a,b) \
({ typeof (a) _a = (a); \
typeof (b) _b = (b); \
if (__builtin_types_compatible_p(typeof(int), _a) && __builtin_types_compatible_p(typeof(int), _a)) DEBUG_INT(_a, _b); \
else if (__builtin_types_compatible_p(typeof(double), _a) && __builtin_types_compatible_p(typeof(double), _a)) DEBUG_DOUBLE(_a, _b); \
else FAIL(_a, _b);
_a > _b ? _a : _b; })