Re: [musl] getpass() feature test macro

["A. Wilcox" <AWilcox@Wilcox-Tech.com>]

On Jul 10, 2025, at 19:58, Haelwenn (lanodan) Monnier <contact@hacktivis.me> wrote:
>> 
>> getpass() was in SUSv2 but already marked legacy: https://pubs.opengroup.org/onlinepubs/007908799/xsh/getpass.html
>> 
>> SUSv2 uses _POSIX_C_SOURCE 199506L: https://pubs.opengroup.org/onlinepubs/007908799/xsh/compilation.html
>> 
>> And expectedly, SUSv3 removed it: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap01.html
>> 
>> Which uses _POSIX_C_SOURCE 200112L: https://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_02.html
> 
> PS: Looking at the PDFs, it has EX shading (extension, seems like early form of XSI shading); so feature macro should be (_XOPEN_SOURCE < 600).
> But `_XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)` seems okay, just potentially misleading due to the !
> 
> Best Regards

Actually, not quite!  That shading is used in SUSv2 for any “feature group” - of which “LEGACY” is one.  A conforming implementation that implements all legacy interfaces is meant to define _XOPEN_LEGACY to something other than -1, and a conforming implementation that does *not* implement legacy interfaces is meant to define _XOPEN_LEGACY to -1.  It does not, afaik, affect which feature macros should be used to request it

They seem to have missed a few “de-shadings”, too, because i.e. getpgid is still shaded as XSI even though it was moved to Base for Issue 5.

As a historical note, SUSv1 (Issue 4, Version 2), which is the oldest standard I still have, shades XSI interfaces as “UX” and the “To Be Withdrawn” (what became LEGACY) interfaces as “EX”; it wasn’t until SUSv2 (Issue 5) when it seems all the shading was unified.  The explanation is found in the change history of <unistd.h> there - these legacy functions were added there but marked as “extensions” because they are “not necessary to implement the base specification”.

Best,
-Anna