[Bug libc/21936] gcc build hangs with glibc 2.26 (conftest about static binaries dlopening themselves)

["felix-glibc at fefe dot de" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21936

--- Comment #2 from Felix von Leitner <felix-glibc at fefe dot de> ---
My understanding is that this is a fairly well-known problem. I found various
bug reports about it, that's why I did not report it earlier.

See for example

  http://www.eglibc.org/archives/issues/msg00086.html
  https://sourceware.org/bugzilla/show_bug.cgi?id=11694
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=584607
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=591544

Here is what happens when I try to compile gcc from svn:

  Revision: 250991

  configure --prefix=/opt/gcc --sysconfdir=/etc --enable-__cxa_atexit
--libdir=/opt/gcc/lib64 --disable-bootstrap --enable-lto --enable-languages=c
--enable-plugin --with-multilib-list=m32,m64,mx32

Here is the last lines of display output:

checking command to parse /tmp/gcc-build/./gcc/nm output from
/tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 object... ok
checking for dlfcn.h... yes
checking for objdir... .libs
checking if /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 supports -fno-rtti
-fno-exceptions... no
checking for /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 option to produce PIC... -fPIC
-DPIC
checking if /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 PIC flag -fPIC -DPIC works...
yes
checking if /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 static flag -static works... yes
checking if /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 supports -c -o file.o... yes
checking if /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 supports -c -o file.o...
(cached) yes
checking whether the /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 linker
(/tmp/gcc-build/./gcc/collect-ld -m elf_x86_64 -m elf_i386) supports shared
libraries... yes
checking whether -lc should be explicitly linked in... no
checking dynamic linker characteristics... GNU/Linux ld.so
checking how to hardcode library paths into programs... immediate
checking for shl_load... no
checking for shl_load in -ldld... no
checking for dlopen... no
checking for dlopen in -ldl... yes
checking whether a program can dlopen itself... yes
checking whether a statically linked program can dlopen itself... 

Here is the conftest.c:

#line 11343 "configure"
#include "confdefs.h"

#if HAVE_DLFCN_H
#include <dlfcn.h>
#endif

#include <stdio.h>

#ifdef RTLD_GLOBAL
#  define LT_DLGLOBAL           RTLD_GLOBAL
#else
#  ifdef DL_GLOBAL
#    define LT_DLGLOBAL         DL_GLOBAL
#  else
#    define LT_DLGLOBAL         0
#  endif
#endif

/* We may have to define LT_DLLAZY_OR_NOW in the command line if we
   find out it does not work in some platform. */
#ifndef LT_DLLAZY_OR_NOW
#  ifdef RTLD_LAZY
#    define LT_DLLAZY_OR_NOW            RTLD_LAZY
#  else
#    ifdef DL_LAZY
#      define LT_DLLAZY_OR_NOW          DL_LAZY
#    else
#      ifdef RTLD_NOW
#        define LT_DLLAZY_OR_NOW        RTLD_NOW
#      else
#        ifdef DL_NOW
#          define LT_DLLAZY_OR_NOW      DL_NOW
#        else
#          define LT_DLLAZY_OR_NOW      0
#        endif
#      endif
#    endif
#  endif
#endif

/* When -fvisbility=hidden is used, assume the code has been annotated
   correspondingly for the symbols needed.  */
#if defined(__GNUC__) && (((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)) ||
(__GNUC__ > 3))
void fnord () __attribute__((visibility("default")));
#endif

void fnord () { int i=42; }
int main ()
{
  void *self = dlopen (0, LT_DLGLOBAL|LT_DLLAZY_OR_NOW);
  int status = 0;

  if (self)
    {
      if (dlsym (self,"fnord"))       status = 1;
      else
        {
          if (dlsym( self,"_fnord"))  status = 2;
          else puts (dlerror ());
        }
      /* dlclose (self); */
    }
  else
    puts (dlerror ());

  return status;
}

It is compiled like this:

  /tmp/gcc-build/./gcc/xgcc -B/tmp/gcc-build/./gcc/
-B/opt/gcc/x86_64-pc-linux-gnu/bin/ -B/opt/gcc/x86_64-pc-linux-gnu/lib/
-isystem /opt/gcc/x86_64-pc-linux-gnu/include -isystem
/opt/gcc/x86_64-pc-linux-gnu/sys-include  -m32 -o conftest -g -pipe -O2 
-DHAVE_DLFCN_H  -Wl,--export-dynamic -static conftest.c -ldl

My first idea was that this was probably because of some files under /opt/gcc
that should not have been there, but it also fails with the regular system gcc
7.1:

  % gcc -m32 -static -o conftest conftest.i -ldl
  /tmp/ccvEWcVy.o: In function `main':   
conftest.c:(.text+0x2c): warning: Using 'dlopen' in statically linked
applications requires at runtime the shared libraries from the glibc version
used for linking
  % ./conftest
[hangs]

Bizarre. I'll attach the conftest.i, but I don't think it will help much.

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