[LEDE-DEV] [PATCH] fix uClibc-ng scanf check

[Alexey Brodkin]

Hi Waldemar,

On Fri, 2016-06-03 at 17:16 +0200, Waldemar Brodkorb wrote:
> Hi Alexey,
> Alexey Brodkin wrote,
> 
> > 
> > Hi Waldemar,
> > 
> > On Fri, 2016-06-03 at 04:23 +0200, Waldemar Brodkorb wrote:
> > > 
> > > uClibc-ng tries to be compatible with GNU libc and defines
> > > __GLIBC__ and pretend to be version 2.2.
> > > We once changed it to 2.10, but then some hard to fix problems
> > > in different software packages (gcc) occured.
> > > It would be better if we disable the special GNU libc checks
> > > for uClibc-ng here. uClibc-ng implements the required scanf
> > > functionality.
> > > 
> > > Signed-off-by: Waldemar Brodkorb <wbx at uclibc-ng.org>
> > > ---
> > >  configure.ac | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/configure.ac b/configure.ac
> > > index f36b18c..4661c0d 100644
> > > --- a/configure.ac
> > > +++ b/configure.ac
> > > @@ -581,7 +581,7 @@ AC_CACHE_VAL([scanf_cv_alloc_modifier],
> > >       #include <stdio.h>
> > >       #include <unistd.h>
> > >  
> > > -     #ifdef __GLIBC__
> > > +     #if defined(__GLIBC__) && !defined(__UCLIBC__)
> > >  
> > >       #if !(__GLIBC_PREREQ(2, 7))
> > >       #error %m is not available
> > Even though this is a very minor and clean change I don't like this
> > approach. We're again implicitly assume something.
> > 
> > IMHO much better approach would be to include a compile test for
> > small source that uses scanf() with "%as"/"%ms".
> > 
> > That way we may remove all dependencies on either GLIBC/UCLIBC/MUSL etc.
> Just for completeness, I saw your other mail already.
> Musl has no problem with this code, because it is util-linux
> fallback code for old GNU libc. Unfortunately it matches the
> pretended version from uClibc-ng. So I think it is the right
> solution, if the fallback code will not be removed.

Thanks for explanation.

-Alexey