虽然是写C++出身,但还真不知道这两个宏是什么作用。查了一下,参见这里。
__STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS are a workaround to allow C++ programs to use stdint.h
macros specified in the C99 standard that aren't in the C++ standard. The macros, such as UINT8_MAX, INT64_MIN,
and INT32_C() may be defined already in C++ applications in other ways. To allow the user to decide
if they want the macros defined as C99 does, many implementations require that __STDC_LIMIT_MACROS
and __STDC_CONSTANT_MACROS be defined before stdint.h is included.This isn't part of the C++ standard, but it has been adopted by more than one implementation.
简单的翻译一下,就是说两个宏__STDC_CONSTANT_MACROS和__STDC_CONSTANT_MACROS,是为在C++中使用C99定义的一些宏,它们定义在<stdint.h>中。这些宏,如:UINT8_MAX, INT64等。虽然这两个宏不是C++标准的内容,但是被不只一种实现采用。
当前在C++11和C11已经不再检测这个宏了,参见这里。