Re: EX_OK collision

[Eric Blake]

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According to Bruno Haible on 3/25/2007 2:22 PM:
> Warning seen on IRIX 6.5:
> 
> "///usr/include/unistd.h", line 43: warning(1047): macro redefined differently
> 
> IRIX 6.5 has two definitions of EX_OK:
>   - one in <unistd.h>, protected with "#if _SGIAPI", as a flag that can be
>     passed to the access() function, with value 020,
>   - one in <sysexits.h>, always active, as an exit code, with value 0.
> 
> Which definition is active, thus depends on the order of inclusion.

Hmm.  EX_OK is not standardized, nor does it fall within the namespace
reserved for use by unistd.h.  But sysexits.h is not even a standardized
header, so it is less likely to be used in a portable program.  Also,
EXIT_SUCCESS of stdlib.h has been standardized.  And looking at the name,
I recognized the _OK suffix more than the EX_ prefix.

> 
> What should we do?
> 
I would go with option d)

Create a replacement <unistd.h> that does
  #if HAVE_SYSEXITS_H
  # include <sysexits.h>
  #endif
  #undef EX_OK
  #include </usr/include/unistd.h>

with no change to sysexits.h

thereby preventing portable programs from falling into the trap of using
non-portable EX_OK as an exit status, while still allowing IRIX-specific
code to query the extended access() attribute.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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