Correct order for including both <cstdio> and <stdio.h>?
c++, gcc, include, stdio
Solution
OK, after some more reasearch I finally came to a conclusion that including the C++ header first, C header later is the correct thing to do. For example, consider the following C++0x header (from gcc):
/usr/include/c++/4.3/tr1_impl/cstdint:
// ...
#define __STDC_LIMIT_MACROS
#define __STDC_CONSTANT_MACROS
#include_next <stdint.h>
// ...
What it does is that it defines two C99 macros, and only then includes the C99 stdint.h header. The reason is that in C99, some of the features of stdint.h are optional, and only available if those macros are defined. However, in C++0x, all stdint.h features are mandatory. Now, if I included the C99 stdint.h first, cstdint later, I wouldn't get the mandatory C++0x features because of the header guards in stdint.h. One could argue that this is the compiler vendor's fault, but that would be incorrect. stdint.h is a system-bundled header (from glibc in this case), which is a C99 header and doesn't know anything about C++0x (it can be an old system, after all) or gcc. The compiler can't really fix all the system headers (in this case to always enable those features in C++ mode), yet it has to provide C++0x support on these systems, so the vendor uses this workaround instead.
Problem
I need to use system-specific functions, e.g. `ftello()` (defined in `stdio.h` as per POSIX standard). I also need to use standard C++ features, e.g. `std::sprintf()` (defined in `cstdio`, as per ISO C++ standard). AFAIK, including only `<cstdio>` doesn't guarantee defining non-standard-C++ stuff, so I guess I have to include both. I've read a long time ago that (for example) with gcc there may be problems with the include file order. So, what is the correct order for including both `<cstdio>` and `<stdio.h>`? I'm looking for a solution which is as cross-platform as possible (at least for gcc, suncc, intel C++/linux and mingw).