Write a macro for C/C++ #include

问题

I work on AS/400 which is sometimes non-POSIX. We also need to compile our code on UNIX. We have an issue with something as simple as #include.

On AS/400, we need to write:

#include "*LIBL/H/MYLIB"

On UNIX, we need to write

#include "MYLIB.H"

At the moment we have this (ugly) block at the top of each C/C++ file:

#ifndef IS_AS400
    #include "*LIBL/H/MYLIB"
    /* others here */
#else
    #include "MYLIB.H"
    /* others here */
#endif

We would like a unified macro. Is this possible? I don't know how to write it.

Ideally, the resulting syntax would be:

SAFE_INCLUDE("MYLIB")

that would expand correctly on each platform.

Please advise.

回答1:

You can simply #include some separate header in every of your source files containing that ugly #ifndef just once. It's a common practice anyway.

回答2:

You can define prefixes for your platform as macro. Like

#define STRINGY(STR) #STR
#define SAFE_INCLUDE(HDR) STRINGY(HDR)

#ifndef IS_AS400
#define SAFE_INCLUDE(LIB) STRINGY(*LIBL/H/##LIB)
#else
#define SAFE_INCLUDE(LIB) STRINGY(LIB##.H)
#endif

and you can use this as

#include SAFE_INCLUDE(MYLIB)

回答3:

There are two better solutions:

Use your Makefiles to properly set a path where compiler looks for includes. For GCC you add to CFLAGS -I <path> (you can do that multiple times).
Wrap the non-compliant libraries with your own header files.

来源：https://stackoverflow.com/questions/6813084/write-a-macro-for-c-c-include

标签

macros

include

ibm-midrange