[Bug libc/29899] Fix for bz#20305 broke glibc on alpha-linux-gnu

["glaubitz at physik dot fu-berlin.de" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29899

--- Comment #5 from John Paul Adrian Glaubitz <glaubitz at physik dot fu-berlin.de> ---
This is the minimum change directly on top the commit that fixes the problem
for me:

diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c
index bd5066fe3b..bc45a6e9d3 100644
--- a/elf/dl-sysdep.c
+++ b/elf/dl-sysdep.c
@@ -115,10 +115,10 @@ _dl_sysdep_start (void **start_argptr,
   user_entry = (ElfW(Addr)) ENTRY_POINT;
   GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. 
*/

-  /* NB: Default to a constant CONSTANT_MINSIGSTKSZ.  */
-  _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
-             "CONSTANT_MINSIGSTKSZ is constant");
-  GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
+  /* /\* NB: Default to a constant CONSTANT_MINSIGSTKSZ.  *\/ */
+  /* _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ), */
+  /*                   "CONSTANT_MINSIGSTKSZ is constant"); */
+  /* GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ; */

   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
     switch (av->a_type)
@@ -184,9 +184,9 @@ _dl_sysdep_start (void **start_argptr,
       case AT_RANDOM:
        _dl_random = (void *) av->a_un.a_val;
        break;
-      case AT_MINSIGSTKSZ:
-   GLRO(dl_minsigstacksize) = av->a_un.a_val;
-   break;
+      /* case AT_MINSIGSTKSZ: */
+      /*     GLRO(dl_minsigstacksize) = av->a_un.a_val; */
+      /*     break; */
       DL_PLATFORM_AUXV
       }

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 9720a4e446..9ead714718 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -536,8 +536,8 @@ struct rtld_global_ro
   /* Cached value of `getpagesize ()'.  */
   EXTERN size_t _dl_pagesize;

-  /* Cached value of `sysconf (_SC_MINSIGSTKSZ)'.  */
-  EXTERN size_t _dl_minsigstacksize;
+  /* /\* Cached value of `sysconf (_SC_MINSIGSTKSZ)'.  *\/ */
+  /* EXTERN size_t _dl_minsigstacksize; */

   /* Do we read from ld.so.cache?  */
   EXTERN int _dl_inhibit_cache;
diff --git a/sysdeps/unix/sysv/linux/sysconf.c
b/sysdeps/unix/sysv/linux/sysconf.c
index 366fcef01e..5a5c89f80e 100644
--- a/sysdeps/unix/sysv/linux/sysconf.c
+++ b/sysdeps/unix/sysv/linux/sysconf.c
@@ -77,12 +77,12 @@ __sysconf (int name)
       }
       break;

-    case _SC_MINSIGSTKSZ:
-      assert (GLRO(dl_minsigstacksize) != 0);
-      return GLRO(dl_minsigstacksize);
+    /* case _SC_MINSIGSTKSZ: */
+    /*   assert (GLRO(dl_minsigstacksize) != 0); */
+    /*   return GLRO(dl_minsigstacksize); */

-    case _SC_SIGSTKSZ:
-      return sysconf_sigstksz ();
+    /* case _SC_SIGSTKSZ: */
+    /*   return sysconf_sigstksz (); */

     default:
       break;

So, my suspicion is that adding the variable _dl_minsigstacksize to struct
rtld_global_ro {} breaks the ABI on Alpha.

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