[glibc] Mark __libc_freeres_fn as used [BZ #27002]

[glibc] Mark __libc_freeres_fn as used [BZ #27002]

[H.J. Lu]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3c1fe20a9f4f6e12a3677ca8a5921ac03976da3b

commit 3c1fe20a9f4f6e12a3677ca8a5921ac03976da3b
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Dec 2 14:26:28 2020 -0800

    Mark __libc_freeres_fn as used [BZ #27002]
    
    GCC 11 with
    
    commit 6fbec038f7a7ddf29f074943611b53210d17c40c
    Author: H.J. Lu <hjl.tools@gmail.com>
    Date:   Mon Feb 3 11:55:43 2020 -0800
    
        Use SHF_GNU_RETAIN to preserve symbol definitions
    
    places used symbols in SECTION_RETAIN sections if assembler supports it.
    Mark __libc_freeres_fn as used to avoid
    
    gconv_dl.c: In function 'free_mem':
    gconv_dl.c:191:1: error: 'do_release_all' without 'used' attribute and 'free_mem' with 'used' attribute are placed in a section with the same name [-Werror=attributes]
      191 | do_release_all (void *nodep)
          | ^~~~~~~~~~~~~~
    In file included from <command-line>:
    gconv_dl.c:202:18: note: 'free_mem' was declared here
      202 | libc_freeres_fn (free_mem)
          |                  ^~~~~~~~
    ./../include/libc-symbols.h:316:15: note: in definition of macro 'libc_freeres_fn'
      316 |   static void name (void)
          |               ^~~~
    cc1: all warnings being treated as errors

Diff:
---
 include/libc-symbols.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index 154a73b5e5..f06ce3053a 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -307,7 +307,7 @@ for linking")
 
 /* Resource freeing functions from libc.so go in this section.  */
 #define __libc_freeres_fn_section \
-  __attribute__ ((section ("__libc_freeres_fn")))
+  __attribute__ ((__used__, section ("__libc_freeres_fn")))
 
 /* Resource freeing functions for libc.so.  */
 #define libc_freeres_fn(name) \