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Re: [PATCH v2 1/2] posix: Add compat glob symbol to not follow dangling

From: Adhemerval Zanella
Subject: Re: [PATCH v2 1/2] posix: Add compat glob symbol to not follow dangling symbols
Date: Tue, 26 Sep 2017 14:40:57 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

On 26/09/2017 11:10, Paul Eggert wrote:
> On 09/26/2017 10:24 AM, Adhemerval Zanella wrote:
>> I see other possible issues that would
>> need to be fixed as well:
>>    * FLEXIBLE_ARRAY_MEMBER definition for !__LIBC.
>>    * __glob_pattern_type duplicated prototype.
>>    * __set_errno and mempcpy definition.
> Thanks for reporting the duplicated prototype; that is a portability
> issue that I fixed in Gnulib by applying the attached patch to Gnulib
> master. Gnulib glob.c already handles FLEXIBLE_ARRAY_MEMBER,
> __set_errno, and mempcpy automatically, because its 'glob' module has
> the modules 'flexmember', 'libc-config', and 'mempcpy' as
> prerequisites, and these supply the necessary definitions.
Thanks, I will sync this change with glibc.

> You can test Gnulib glob.c's portabililty by running this shell
> command in Gnulib's top directory:
> ./gnulib-tool --create-testdir --dir foo glob
> and then by copying the newly-created 'foo' directory to the platform
> of your choice and running './configure; make check' there.
> Gnu Make does not use Gnulib. Instead, it ships an old version of
> glob.c, which it took directly from glibc in 1999; this all predates
> Gnulib. If GNU Make ever updates to a more-modern glob.c I suggest
> that it use the Gnulib glob module, along with that module's
> prerequisites. I could help do that, if the GNU Make maintainer wants
> to go that route. [I'll CC: this to bug-make to give its maintainer a
> heads-up about this libc-alpha discussion, which can be followed from
> here:
> https://sourceware.org/ml/libc-alpha/2017-09/msg00972.html

Besides update GNU make glob implementation I think it should also update
its configure.ac to accept not only _GNU_GLOB_INTERFACE_VERSION equal
to 1, but also _GNU_GLOB_INTERFACE_VERSION to 2 now that your suggestion [1]
has been fixed.

[1] http://lists.gnu.org/archive/html/bug-make/2017-09/msg00014.html

> ]
>> I could build gnumake with forced internal glob implementation
>> (make_cv_sys_gnu_glob=no) with the patch following patch.  Looking
>> gnulib I am not sure if the correct way to use mempcpy for !_LIBC.
> Sorry, but I'm confused by that patch (quoted below). It is a patch to
> glibc, so at first I assumed that you applied it to a copy of the
> glibc source, built a new glibc with it, and then used the newly-built
> glibc to configure and build GNU Make 4.2.1.  But that assumption
> cannot be right, since the patch modifies only code that is unused
> when building glibc. And one cannot simply copy current or patched
> glibc posix/glob.c into make's lib/glob.c, as (among other things)
> glibc's posix/glob.c includes <flexmember.h> when compiled outside of
> glibc, and GNU Make does not have that include file. So how did you
> use this patch?
Sorry if I were not explicit, the patch is indeed against glibc and what
I did was
basically copy glob.c and all required files (flexmember.h and
on glob folder. It is just a ad hoc way to verify if its build correctly.

>> diff --git a/posix/glob.c b/posix/glob.c
>> index 98122dac88..31e3aba4dd 100644
>> --- a/posix/glob.c
>> +++ b/posix/glob.c
>> @@ -65,11 +65,15 @@
>>   # define __stat64(fname, buf)   stat (fname, buf)
>>   # define __fxstatat64(_, d, f, st, flag) fstatat (d, f, st, flag)
>>   # define struct_stat64          struct stat
>> -# ifndef __MVS__
>> -#  define __alloca              alloca
>> -# endif
>> +# define __alloca               alloca
>>   # define __readdir              readdir
>>   # define COMPILE_GLOB64
>> +static inline void *
>> +mempcpy (void *dest, const void *src, size_t n)
>> +{
>> +  return memcpy (dest, src, n) + n;
>> +}
>>   #endif /* _LIBC */
>>     #include <fnmatch.h>
>> @@ -230,8 +234,6 @@ glob_use_alloca (size_t alloca_used, size_t len)
>>   static int glob_in_dir (const char *pattern, const char *directory,
>>                          int flags, int (*errfunc) (const char *, int),
>>                          glob_t *pglob, size_t alloca_used);
>> -extern int __glob_pattern_type (const char *pattern, int quote)
>> -    attribute_hidden;
>>     static int prefix_array (const char *prefix, char **array, size_t
>> n) __THROWNL;
>>   static int collated_compare (const void *, const void *) __THROWNL;

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