Problems with #import <stdarg.h>

Problems with #import <stdarg.h>

[Ronald Pijnacker]

Hi all,

When I include stdarg.h after stdio.h using objc's #import I get the error:

$ gcc -c stdarg.m
stdarg.m: In function 'func':
stdarg.m:6: error: 'va_list' undeclared (first use in this function)
stdarg.m:6: error: (Each undeclared identifier is reported only once
stdarg.m:6: error: for each function it appears in.)
stdarg.m:6: error: expected ';' before 'ap'
stdarg.m:7: error: 'ap' undeclared (first use in this function)

when I switch the two around, it is ok.

Thanks,

Ronald

RE: Problems with #import <stdarg.h>

[John (Eljay) Love-Jensen]

Hi Ronald,

I believe* all the operating system provided headers (such as the Standard C Library ones) expected to be #include'd (which uses the C protocol for the preprocessor), not #import'd (the ObjC protocol for the preprocessor).

Using #import can interfere with their multi-include logic.  The reason for the multi-include logic is historical/legacy, evolutionary, backwards compatibility, and also involves ISO 9899 standardization (both 1989 and 1999).  And for some headers, which are more intimately tied to the operating system than the Standard C Library, there may be some POSIX (IEEE Std 1003) contortions as well or UNIX 2003 contortions.  It's hard to please everyone.

In theory, they could be made to be #import savvy as well, but those headers are really C headers, not ObjC headers.  (Often they have allowances incorporated to be used as-is for C++.  But C++ compilation units really should use <cstdarg> and <cstdio> rather than the raw C <stdarg.h> and <stdio.h> anyway.)

HTH,
--Eljay

* I may be mistaken.