🚀 go-pugleaf

In article 181@steiny.com, steiny@steiny.com (Don Steiny) writes:
>I have been having a few problems with gcc (bit of bad luck on my part, 
>by some strange coincidence it will not compile any non-trivial program
>I try :-().
>
>The first problem is that it does not seem to find the definition for 
>stack_t in signal.h.   According to the #if I need to have 
>
>#if !defined (__STRICT_ANSI__) && !defined(_POSIX_SOURCE)
>
>before the code in the gcc-include/signal.h is included.   But why would
>_POSIX_SOURCE be undefined?   

Because you haven't defined it: _POSIX_SOURCE is a feature test macro.

In a strictly conforming ANSI C environment the standard headers (those
listed in section 7 of the standard) should not define any symbols or
prototypes that are not defined in the standard.

Historically, UNIX implementations have defined symbols and prototypes in
these headers that are not defined in ANSI standard C.  Feature test macros
are used to keep UNIX interfaces consistent with ANSI C.  If you want symbols
and prototypes to be imported from that standard headers that are not part of
the ANSI C standard you must define an appropriate feature test macro.  This way
you know that if you do not define a feature test macro your program is using
only ANSI C facilities (provided it compiles of course).

_POSIX_SOURCE is the feature test macro for the facilities in the POSIX.1
standard.  If _POSIX_SOURCE is defined your program will import the ANSI C
facilities and the POSIX.1 facilities but nothing else.  POSIX.2 introduced
the alternative macro _POSIX_C_SOURCE.  If _POSIX_C_SOURCE is defined to be
1 you get ANSI C and POSIX.1 facilities (the same as defining _POSIX_SOURCE);
if POSIX_C_SOURCE is 2 you get the POSIX.2 facilities as well.

Other UNIX standards have their own feature test macros to activate features
that are not ANSI C or POSIX.  For example you can define _AES_SOURCE on an
OSF/1 system to activate all of the features in the OSF AES or define 
_XOPEN_SOURCE on an XPG3 compliant system to activate features in XPG3.

Now stack_t is not an ANSI C type nor is it a POSIX.1 type so you should not
be able to import it into a strictly conforming program, even if _POSIX_SOURCE
is defined.  If you need stack_t you either need to find a magic feature test
macro that enables its definition or turn off strict ANSI checking.

	Chris Flatters
	cflatter@nrao.edu