在另一个宏中使用字符串宏[复制]

通常情况下,处理printf样式的格式比较容易 "Too many operations! Only the first %u were applied"

#define STR(x) STR2(x)
#define STR2(x) #x
#define MAX_OPERATION_COUNT 10
#define MSG_TOO_MANY_OPERATIONS "Too many operations! Only the first " STR(MAX_OPERATION_COUNT) " were applied."

#define STRINGYFY(x) # x
#define PASTE_AS_STRING(s) STRINGYFY(s)

#define MAX_OPERATION_COUNT 10
#define MANY_OPERATION_COUNT 2

#define MSG_TOO_MANY_OPERATIONS_TEMPLATE(n) \
  "Too many operations! Only the first" PASTE_AS_STRING(n) " were applied."

#define MSG_TOO_MANY_OPERATIONS \
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MAX_OPERATION_COUNT)
#define MSG_MUCH_TOO_MANY_OPERATIONS \
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MANY_OPERATION_COUNT)

(刚才看到了 Matt's answer

要定义数组

const char MSG_TOO_MANY_OPERATIONS[] = 
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MAX_OPERATION_COUNT)
const char MSG_MUCH_TOO_MANY_OPERATIONS[] =
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MANY_OPERATION_COUNT)

或者定义指针呢

const char * MSG_TOO_MANY_OPERATIONS = 
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MAX_OPERATION_COUNT)
const char * MSG_MUCH_TOO_MANY_OPERATIONS =
  MSG_TOO_MANY_OPERATIONS_TEMPLATE(MANY_OPERATION_COUNT)

#define MAX_OPERATION_COUNT "10"
#define MSG_TOO_MANY_OPERATIONS "Too many operations! Only the first " MAX_OPERATION_COUNT " were applied."

你可以做:

#define FOO "1"
#define BAR "How many foos? " FOO " foo.\n"

BAR 现在扩展到

"How many foos? " "1" " foo.\n"