Re: [PATCH 6/6] Add configure check for members of dirent for use in io/readdir.c

[Dave Chinner <david@xxxxxxxxxxxxx>]

On Tue, Jan 12, 2016 at 10:37:11PM +0100, Felix Janda wrote:
> Dave Chinner wrote:
> > On Tue, Jan 12, 2016 at 09:00:22PM +0100, Felix Janda wrote:
> > > Signed-off-by: Felix Janda <felix.janda@xxxxxxxxx>
> > > ---
> > >  configure.ac         |  7 +++++++
> > >  include/builddefs.in |  4 ++++
> > >  io/Makefile          | 10 ++++++++++
> > >  3 files changed, 21 insertions(+)
> > > 
> > > diff --git a/configure.ac b/configure.ac
> > > index feee50a..3d6443a 100644
> > > --- a/configure.ac
> > > +++ b/configure.ac
> > > @@ -135,5 +135,12 @@ AC_CHECK_SIZEOF([char *])
> > >  AC_TYPE_UMODE_T
> > >  AC_MANUAL_FORMAT
> > >  
> > > +AC_CHECK_MEMBERS([struct dirent.d_reclen],[],[],[[#include <dirent.h>]])
> > > +AC_SUBST(ac_cv_member_struct_dirent_d_reclen)
> > > +AC_CHECK_MEMBERS([struct dirent.d_off],[],[],[[#include <dirent.h>]])
> > > +AC_SUBST(ac_cv_member_struct_dirent_d_off)
> > > +AC_CHECK_MEMBERS([struct dirent.d_type],[],[],[[#include <dirent.h>]])
> > > +AC_SUBST(ac_cv_member_struct_dirent_d_type)
> > > +
> > >  AC_CONFIG_FILES([include/builddefs])
> > >  AC_OUTPUT
> > > diff --git a/include/builddefs.in b/include/builddefs.in
> > > index b5ce336..67d963c 100644
> > > --- a/include/builddefs.in
> > > +++ b/include/builddefs.in
> > > @@ -109,6 +109,10 @@ HAVE_FLS = @have_fls@
> > >  HAVE_FSETXATTR = @have_fsetxattr@
> > >  HAVE_MREMAP = @have_mremap@
> > >  
> > > +HAVE_STRUCT_DIRENT_D_RECLEN = @ac_cv_member_struct_dirent_d_reclen@
> > > +HAVE_STRUCT_DIRENT_D_OFF = @ac_cv_member_struct_dirent_d_off@
> > > +HAVE_STRUCT_DIRENT_D_TYPE = @ac_cv_member_struct_dirent_d_type@
> > > +
> > >  GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
> > >  #           -Wbitwise -Wno-transparent-union -Wno-old-initializer 
> > > -Wno-decl
> > >  
> > > diff --git a/io/Makefile b/io/Makefile
> > > index 0b53f41..9574168 100644
> > > --- a/io/Makefile
> > > +++ b/io/Makefile
> > > @@ -94,6 +94,16 @@ ifeq ($(HAVE_MREMAP),yes)
> > >  LCFLAGS += -DHAVE_MREMAP
> > >  endif
> > >  
> > > +ifeq ($(HAVE_STRUCT_DIRENT_D_RECLEN),yes)
> > > +LCFLAGS += -D_DIRENT_HAVE_D_RECLEN
> > > +endif
> > 
> > The C library should be defining these if those fields are
> > supported, right?
> 
> It is strongly advised not to use these non-standard fields of dirent.

We're not writing POSIX applications here - this is a diagnostic
tool so if we are running on linux we need to expose them.

If we've got linux C libraries that don't provide feature macros for
the fields in the linux_dirent eposed by readdir(3), then I guess
we're stuck with having to play autoconf games, eh?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx