I see this in the standard C++ libraries for my system, as well as some of the headers in a library I'm using.
What are the semantics of these two definitions? Is there a good reference for #defines like this other than the source itself?
I see this in the standard C++ libraries for my system, as well as some of the headers in a library I'm using.
What are the semantics of these two definitions? Is there a good reference for #defines like this other than the source itself?
The macros are not part of the C++ standard and are probably used for internal purposes in your C++ implementation. If you want to know more about them, you should ask a question with atag that indicates what that implementation is.
In stdint.h
under C++, they control whether to define macros like INT32_MAX
or INT32_C(v)
. See your platform's stdint.h
for additional information.
__STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS are a workaround to allow C++ programs to use 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.