Date: Thu, 14 Jan 2016 21:27:13 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] add _DIRENT_HAVE_D_* constants to dirent.h On Thu, Jan 14, 2016 at 05:44:49PM -0500, Rich Felker wrote: > On Wed, Jan 13, 2016 at 07:09:19PM +0100, Felix Janda wrote: > > they can be used for checking existence of non-standard fields of > > struct dirent, are used by various programs to avoid configure > > checks and are at least present on glibc, uclibc, dietlibc and > > newlib. > > --- > > The motivation for this patch is > > > > http://oss.sgi.com/archives/xfs/2016-01/msg00388.html > > --- > > include/dirent.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/include/dirent.h b/include/dirent.h > > index 5aa8510..b2ffe8a 100644 > > --- a/include/dirent.h > > +++ b/include/dirent.h > > @@ -57,6 +57,9 @@ int getdents(int, struct dirent *, size_t); > > #endif > > > > #ifdef _GNU_SOURCE > > +#define _DIRENT_HAVE_D_OFF > > +#define _DIRENT_HAVE_D_RECLEN > > +#define _DIRENT_HAVE_D_TYPE > > int versionsort(const struct dirent **, const struct dirent **); > > #endif > > I like the concept of defining macros to publish the availability of > extensions like this, but I don't think they should be dependent on > _GNU_SOURCE. At the very least they should also be available under > _DEFAULT_SOURCE (_BSD_SOURCE), but since they're in the reserved > namespace (underscore followed by capital) I'd prefer to have them > exposed unconditionally. > > I'm also skeptical of whether d_off and d_reclen should be promoted as > public APIs. They don't seem to be useful (unlike d_type which is > highly useful) and may lock down some assumptions about > implementation. Perhaps to make a discussion of this more concrete: is there other software that's using the d_reclen or d_off fields conditionally on having the above macros defined? What is is using them for? I read the above-linked mailing list discussion and I think the autoconf test is a better approach than depending on the macros (since they're not present on older musl or on other non-glibc libcs/systems) but we should probably add at least _DIRENT_HAVE_D_TYPE and perhaps the others too. Rich
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