Solaris 10 - SPARC - SUN编译器。
测试代码：
#include <stdio.h>
static int parseMonth(const char *input) {
int rv=-1;
int inputInt=0;
int i=0;
for(i=0; i<4 && input[i]; i++) {
inputInt = (inputInt << 8) | input[i];
}
switch(inputInt) {
case 'Jan/': rv=0; break;
case 'Feb/': rv=1; break;
case 'Mar/': rv=2; break;
case 'Apr/': rv=3; break;
case 'May/': rv=4; break;
case 'Jun/': rv=5; break;
case 'Jul/': rv=6; break;
case 'Aug/': rv=7; break;
case 'Sep/': rv=8; break;
case 'Oct/': rv=9; break;
case 'Nov/': rv=10; break;
case 'Dec/': rv=11; break;
}
return rv;
}
static const struct
{
char *data;
int result;
} test_case[] =
{
{ "Jan/", 0 },
{ "Feb/", 1 },
{ "Mar/", 2 },
{ "Apr/", 3 },
{ "May/", 4 },
{ "Jun/", 5 },
{ "Jul/", 6 },
{ "Aug/", 7 },
{ "Sep/", 8 },
{ "Oct/", 9 },
{ "Nov/", 10 },
{ "Dec/", 11 },
{ "aJ/n", -1 },
};
#define DIM(x) (sizeof(x)/sizeof(*(x)))
int main(void)
{
size_t i;
int result;
for (i = 0; i < DIM(test_case); i++)
{
result = parseMonth(test_case[i].data);
if (result != test_case[i].result)
printf("!! FAIL !! %s (got %d, wanted %d)\n",
test_case[i].data, result, test_case[i].result);
}
return(0);
}
结果（GCC 3.4.2 和 Sun）：
$ gcc -O xx.c -o xx
xx.c:14:14: warning: multi-character character constant
xx.c:15:14: warning: multi-character character constant
xx.c:16:14: warning: multi-character character constant
xx.c:17:14: warning: multi-character character constant
xx.c:18:14: warning: multi-character character constant
xx.c:19:14: warning: multi-character character constant
xx.c:20:14: warning: multi-character character constant
xx.c:21:14: warning: multi-character character constant
xx.c:22:14: warning: multi-character character constant
xx.c:23:14: warning: multi-character character constant
xx.c:24:14: warning: multi-character character constant
xx.c:25:14: warning: multi-character character constant
$ ./xx
$ cc -o xx xx.c
$ ./xx
$
请注意，最后一个测试用例仍然通过了——也就是说，它生成了-1。
下面是parseMonth()的修订版，更加详细，可以在GCC和Sun C编译器下正常工作：
/* MONTH_CODE("Jan/") does not reduce to an integer constant */
#define MONTH_CODE(x) ((((((x[0]<<8)|x[1])<<8)|x[2])<<8)|x[3])
#define MONTH_JAN (((((('J'<<8)|'a')<<8)|'n')<<8)|'/')
#define MONTH_FEB (((((('F'<<8)|'e')<<8)|'b')<<8)|'/')
#define MONTH_MAR (((((('M'<<8)|'a')<<8)|'r')<<8)|'/')
#define MONTH_APR (((((('A'<<8)|'p')<<8)|'r')<<8)|'/')
#define MONTH_MAY (((((('M'<<8)|'a')<<8)|'y')<<8)|'/')
#define MONTH_JUN (((((('J'<<8)|'u')<<8)|'n')<<8)|'/')
#define MONTH_JUL (((((('J'<<8)|'u')<<8)|'l')<<8)|'/')
#define MONTH_AUG (((((('A'<<8)|'u')<<8)|'g')<<8)|'/')
#define MONTH_SEP (((((('S'<<8)|'e')<<8)|'p')<<8)|'/')
#define MONTH_OCT (((((('O'<<8)|'c')<<8)|'t')<<8)|'/')
#define MONTH_NOV (((((('N'<<8)|'o')<<8)|'v')<<8)|'/')
#define MONTH_DEC (((((('D'<<8)|'e')<<8)|'c')<<8)|'/')
static int parseMonth(const char *input) {
int rv=-1;
int inputInt=0;
int i=0;
for(i=0; i<4 && input[i]; i++) {
inputInt = (inputInt << 8) | input[i];
}
switch(inputInt) {
case MONTH_JAN: rv=0; break;
case MONTH_FEB: rv=1; break;
case MONTH_MAR: rv=2; break;
case MONTH_APR: rv=3; break;
case MONTH_MAY: rv=4; break;
case MONTH_JUN: rv=5; break;
case MONTH_JUL: rv=6; break;
case MONTH_AUG: rv=7; break;
case MONTH_SEP: rv=8; break;
case MONTH_OCT: rv=9; break;
case MONTH_NOV: rv=10; break;
case MONTH_DEC: rv=11; break;
}
return rv;
}
static const struct
{
char *data;
int result;
} test_case[] =
{
{ "Jan/", 0 },
{ "Feb/", 1 },
{ "Mar/", 2 },
{ "Apr/", 3 },
{ "May/", 4 },
{ "Jun/", 5 },
{ "Jul/", 6 },
{ "Aug/", 7 },
{ "Sep/", 8 },
{ "Oct/", 9 },
{ "Nov/", 10 },
{ "Dec/", 11 },
{ "aJ/n", -1 },
{ "/naJ", -1 },
};
#define DIM(x) (sizeof(x)/sizeof(*(x)))
int main(void)
{
size_t i;
int result;
for (i = 0; i < DIM(test_case); i++)
{
result = parseMonth(test_case[i].data);
if (result != test_case[i].result)
printf("!! FAIL !! %s (got %d, wanted %d)\n",
test_case[i].data, result, test_case[i].result);
}
return(0);
}
我想使用MONTH_CODE()函数，但编译器没有配合。
