Add tests for namespace for static linking.

One thing we currently try to ensure manually is that glibc is
namespace-clean for static linking; that is, if you only use features
from a particular standard (including the set of features exposed by
headers given feature test macros such as _DEFAULT_SOURCE that don't
correspond to any written standard), the library objects brought in by
the static linker will not define or use (strong) names that are
reserved to the user in that standard.

This patch implements automatic tests for this, using the same set of
standards as for the header conformance tests (it would, however, be
easy to add more standards for this testing, without them needing to
have the definitions of expected header contents for the header
tests).  The tests are based on the functions declared in each header,
as extracted using GCC's -aux-info option.  The following comment from
linknamespace.pl explains the caveats around this approach:

Here's an example of the output for ISO (C90) assert.h, from before my
recent fixes and whitelisting of cases that seem more complicated to
fix:

[initial] __assert_fail -> [libc.a(assert.o)] free -> [libc.a(malloc.o)] __get_nprocs -> [libc.a(getsysstats.o)] fgets_unlocked
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] __libc_setlocale_lock -> [libc.a(setlocale.o)] _nl_archive_subfreeres -> [libc.a(loadarchive.o)] __sysconf -> [libc.a(sysconf.o)] __tzname_max -> [libc.a(tzset.o)] __tzfile_compute -> [libc.a(tzfile.o)] fileno
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] __libc_setlocale_lock -> [libc.a(setlocale.o)] _nl_archive_subfreeres -> [libc.a(loadarchive.o)] __sysconf -> [libc.a(sysconf.o)] __tzname_max -> [libc.a(tzset.o)] __tzfile_compute -> [libc.a(tzfile.o)] fread_unlocked
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] __libc_setlocale_lock -> [libc.a(setlocale.o)] _nl_archive_subfreeres -> [libc.a(loadarchive.o)] __sysconf -> [libc.a(sysconf.o)] __tzname_max -> [libc.a(tzset.o)] __tzfile_compute -> [libc.a(tzfile.o)] ftello
[initial] __assert_fail -> [libc.a(assert.o)] free -> [libc.a(malloc.o)] malloc_info
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] __libc_setlocale_lock -> [libc.a(setlocale.o)] _nl_default_locale_path -> [libc.a(findlocale.o)] memmem
[initial] __assert_perror_fail -> [libc.a(assert-perr.o)] __strerror_r -> [libc.a(_strerror.o)] mempcpy
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] _nl_find_domain -> [libc.a(finddomain.o)] _nl_expand_alias -> [libc.a(localealias.o)] qsort -> [libc.a(msort.o)] qsort_r
[initial] __assert_fail -> [libc.a(assert.o)] _dl_pagesize -> [libc.a(dl-support.o)] __rawmemchr -> [libc.a(rawmemchr.o)] rawmemchr
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] __getcwd -> [libc.a(getcwd.o)] rewinddir
[initial] __assert_fail -> [libc.a(assert.o)] stderr
[initial] __assert_fail -> [libc.a(assert.o)] stderr -> [libc.a(stdio.o)] stdin
[initial] __assert_fail -> [libc.a(assert.o)] stderr -> [libc.a(stdio.o)] stdout
[initial] __assert_fail -> [libc.a(assert.o)] __dcgettext -> [libc.a(dcgettext.o)] __dcigettext -> [libc.a(dcigettext.o)] stpcpy
[initial] __assert_fail -> [libc.a(assert.o)] __fxprintf -> [libc.a(fxprintf.o)] _IO_vfprintf -> [libc.a(vfprintf.o)] __printf_fp -> [libc.a(printf_fp.o)] wmemset

Of the 161 XFAILs, seven are the inevitable varargs.h and ndbm.h
failures; I think the remaining 154 mostly represent genuine bugs in
glibc that should mostly be straightforward to fix (probably rather
fewer than 154 bugs - issues generally affect multiple headers, for
multiple standards).  (When fixing, of course you need to file a bug
in Bugzilla, and check for the possibility that the header
conditionals are what's incorrect - that the first listed symbol
shouldn't have been declared, or that the symbol finally brought in
should have been declared.)

	* conform/GlibcConform.pm: New file.
	* conform/conformtest.pl: Use GlibcConform module.
	* conform/linknamespace.pl: New file.
	* conform/list-header-symbols.pl: Likewise.
	* conform/Makefile (linknamespace-symlists-base): New variable.
	(linknamespace-symlists-tests): Likewise.
	(linknamespace-header-base): Likewise.
	(linknamespace-header-tests): Likewise.
	(tests-special): Add new tests.
	($(linknamespace-symlists-tests)): New rule.
	(linknamespace-libs): New variable.
	($(objpfx)symlist-stdlibs): New rule.
	($(linknamespace-header-tests)): Likewise.
	(test-xfail-XPG3/varargs.h/linknamespace): New variable.
	(test-xfail-XPG4/varargs.h/linknamespace): Likewise.
	(test-xfail-UNIX98/varargs.h/linknamespace): Likewise.
	(test-xfail-XPG4/ndbm.h/linknamespace): Likewise.
	(test-xfail-UNIX98/ndbm.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/ndbm.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/ndbm.h/linknamespace): Likewise.
	(test-xfail-ISO/math.h/linknamespace): Likewise.
	(test-xfail-ISO/signal.h/linknamespace): Likewise.
	(test-xfail-ISO/stdio.h/linknamespace): Likewise.
	(test-xfail-ISO/time.h/linknamespace): Likewise.
	(test-xfail-ISO99/complex.h/linknamespace): Likewise.
	(test-xfail-ISO99/ctype.h/linknamespace): Likewise.
	(test-xfail-ISO99/math.h/linknamespace): Likewise.
	(test-xfail-ISO99/signal.h/linknamespace): Likewise.
	(test-xfail-ISO99/stdio.h/linknamespace): Likewise.
	(test-xfail-ISO99/tgmath.h/linknamespace): Likewise.
	(test-xfail-ISO11/complex.h/linknamespace): Likewise.
	(test-xfail-ISO11/ctype.h/linknamespace): Likewise.
	(test-xfail-ISO11/math.h/linknamespace): Likewise.
	(test-xfail-ISO11/signal.h/linknamespace): Likewise.
	(test-xfail-ISO11/stdio.h/linknamespace): Likewise.
	(test-xfail-ISO11/tgmath.h/linknamespace): Likewise.
	(test-xfail-XPG3/ctype.h/linknamespace): Likewise.
	(test-xfail-XPG3/fnmatch.h/linknamespace): Likewise.
	(test-xfail-XPG3/glob.h/linknamespace): Likewise.
	(test-xfail-XPG3/math.h/linknamespace): Likewise.
	(test-xfail-XPG3/regex.h/linknamespace): Likewise.
	(test-xfail-XPG3/search.h/linknamespace): Likewise.
	(test-xfail-XPG3/stdio.h/linknamespace): Likewise.
	(test-xfail-XPG3/time.h/linknamespace): Likewise.
	(test-xfail-XPG3/unistd.h/linknamespace): Likewise.
	(test-xfail-XPG3/wordexp.h/linknamespace): Likewise.
	(test-xfail-XPG4/ctype.h/linknamespace): Likewise.
	(test-xfail-XPG4/fmtmsg.h/linknamespace): Likewise.
	(test-xfail-XPG4/fnmatch.h/linknamespace): Likewise.
	(test-xfail-XPG4/glob.h/linknamespace): Likewise.
	(test-xfail-XPG4/grp.h/linknamespace): Likewise.
	(test-xfail-XPG4/libgen.h/linknamespace): Likewise.
	(test-xfail-XPG4/math.h/linknamespace): Likewise.
	(test-xfail-XPG4/netdb.h/linknamespace): Likewise.
	(test-xfail-XPG4/pwd.h/linknamespace): Likewise.
	(test-xfail-XPG4/regex.h/linknamespace): Likewise.
	(test-xfail-XPG4/search.h/linknamespace): Likewise.
	(test-xfail-XPG4/stdio.h/linknamespace): Likewise.
	(test-xfail-XPG4/stdlib.h/linknamespace): Likewise.
	(test-xfail-XPG4/sys/mman.h/linknamespace): Likewise.
	(test-xfail-XPG4/sys/statvfs.h/linknamespace): Likewise.
	(test-xfail-XPG4/syslog.h/linknamespace): Likewise.
	(test-xfail-XPG4/time.h/linknamespace): Likewise.
	(test-xfail-XPG4/unistd.h/linknamespace): Likewise.
	(test-xfail-XPG4/wordexp.h/linknamespace): Likewise.
	(test-xfail-POSIX/aio.h/linknamespace): Likewise.
	(test-xfail-POSIX/fnmatch.h/linknamespace): Likewise.
	(test-xfail-POSIX/glob.h/linknamespace): Likewise.
	(test-xfail-POSIX/math.h/linknamespace): Likewise.
	(test-xfail-POSIX/mqueue.h/linknamespace): Likewise.
	(test-xfail-POSIX/pthread.h/linknamespace): Likewise.
	(test-xfail-POSIX/regex.h/linknamespace): Likewise.
	(test-xfail-POSIX/sched.h/linknamespace): Likewise.
	(test-xfail-POSIX/semaphore.h/linknamespace): Likewise.
	(test-xfail-POSIX/sys/mman.h/linknamespace): Likewise.
	(test-xfail-POSIX/time.h/linknamespace): Likewise.
	(test-xfail-POSIX/unistd.h/linknamespace): Likewise.
	(test-xfail-POSIX/wordexp.h/linknamespace): Likewise.
	(test-xfail-UNIX98/aio.h/linknamespace): Likewise.
	(test-xfail-UNIX98/ctype.h/linknamespace): Likewise.
	(test-xfail-UNIX98/fmtmsg.h/linknamespace): Likewise.
	(test-xfail-UNIX98/fnmatch.h/linknamespace): Likewise.
	(test-xfail-UNIX98/glob.h/linknamespace): Likewise.
	(test-xfail-UNIX98/grp.h/linknamespace): Likewise.
	(test-xfail-UNIX98/libgen.h/linknamespace): Likewise.
	(test-xfail-UNIX98/math.h/linknamespace): Likewise.
	(test-xfail-UNIX98/mqueue.h/linknamespace): Likewise.
	(test-xfail-UNIX98/netdb.h/linknamespace): Likewise.
	(test-xfail-UNIX98/pthread.h/linknamespace): Likewise.
	(test-xfail-UNIX98/pwd.h/linknamespace): Likewise.
	(test-xfail-UNIX98/regex.h/linknamespace): Likewise.
	(test-xfail-UNIX98/sched.h/linknamespace): Likewise.
	(test-xfail-UNIX98/search.h/linknamespace): Likewise.
	(test-xfail-UNIX98/semaphore.h/linknamespace): Likewise.
	(test-xfail-UNIX98/stdio.h/linknamespace): Likewise.
	(test-xfail-UNIX98/stdlib.h/linknamespace): Likewise.
	(test-xfail-UNIX98/sys/mman.h/linknamespace): Likewise.
	(test-xfail-UNIX98/sys/statvfs.h/linknamespace): Likewise.
	(test-xfail-UNIX98/syslog.h/linknamespace): Likewise.
	(test-xfail-UNIX98/time.h/linknamespace): Likewise.
	(test-xfail-UNIX98/unistd.h/linknamespace): Likewise.
	(test-xfail-UNIX98/wchar.h/linknamespace): Likewise.
	(test-xfail-UNIX98/wordexp.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/aio.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/complex.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/fcntl.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/fmtmsg.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/fnmatch.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/glob.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/grp.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/libgen.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/math.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/mqueue.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/net/if.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/netdb.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/pthread.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/pwd.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/regex.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/search.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/semaphore.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/signal.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/spawn.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/stdlib.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/sys/mman.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/sys/statvfs.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/sys/wait.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/syslog.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/tgmath.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/time.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/ucontext.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/unistd.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/wordexp.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/aio.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/complex.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/ctype.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/dirent.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/fcntl.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/grp.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/math.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/mqueue.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/net/if.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/netdb.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/pthread.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/regex.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/semaphore.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/spawn.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/sys/mman.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/sys/statvfs.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/tgmath.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/time.h/linknamespace): Likewise.
	(test-xfail-POSIX2008/unistd.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/aio.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/complex.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/dirent.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/fcntl.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/fmtmsg.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/grp.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/libgen.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/math.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/mqueue.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/net/if.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/netdb.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/pthread.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/pwd.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/regex.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/search.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/semaphore.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/spawn.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/sys/mman.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/sys/statvfs.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/syslog.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/tgmath.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/time.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/unistd.h/linknamespace): Likewise.

1 files changed, 241 insertions, 0 deletions

diff --git a/conform/linknamespace.pl b/conform/linknamespace.pl
new file mode 100644
index 0000000000..fd8c3dc81b
--- /dev/null
+++ b/conform/linknamespace.pl
@@ -0,0 +1,241 @@
+#! /usr/bin/perl
+
+# Check that use of symbols declared in a given header does not result
+# in any symbols being brought in that are not reserved with external
+# linkage for the given standard.
+
+# Copyright (C) 2014 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+use GlibcConform;
+use Getopt::Long;
+
+GetOptions ('header=s' => \$header, 'standard=s' => \$standard,
+	    'flags=s' => \$flags, 'cc=s' => \$CC, 'tmpdir=s' => \$tmpdir,
+	    'stdsyms=s' => \$stdsyms_file, 'libsyms=s' => \$libsyms_file,
+	    'readelf=s' => \$READELF);
+
+# Load the list of symbols that are OK.
+%stdsyms = ();
+open (STDSYMS, "<$stdsyms_file") || die ("open $stdsyms_file: $!\n");
+while (<STDSYMS>) {
+  chomp;
+  $stdsyms{$_} = 1;
+}
+close (STDSYMS) || die ("close $stdsyms_file: $!\n");
+
+# The following whitelisted symbols are also allowed for now.
+#
+# * Bug 15421: lgamma wrongly sets signgam for ISO C.
+#
+# * Bug 17576: stdin, stdout, stderr only reserved with external
+# linkage when stdio.h included (and possibly not then), not
+# generally.
+#
+# * False positive: matherr only used conditionally.
+#
+@whitelist = qw(signgam stdin stdout stderr matherr);
+foreach my $sym (@whitelist) {
+  $stdsyms{$sym} = 1;
+}
+
+# Return information about GLOBAL and WEAK symbols listed in readelf
+# -s output.
+sub list_syms {
+  my ($syms_file) = @_;
+  open (SYMS, "<$syms_file") || die ("open $syms_file: $!\n");
+  my ($file) = $syms_file;
+  my (@ret) = ();
+  while (<SYMS>) {
+    chomp;
+    if (/^File: (.*)/) {
+      $file = $1;
+      $file =~ s|^.*/||;
+      next;
+    }
+    s/^\s*//;
+    my (@fields) = split (/\s+/, $_);
+    if (@fields < 8) {
+      next;
+    }
+    my ($bind) = $fields[4];
+    my ($ndx) = $fields[6];
+    my ($sym) = $fields[7];
+    if ($bind ne "GLOBAL" && $bind ne "WEAK") {
+      next;
+    }
+    if ($sym !~ /^\w+$/) {
+      next;
+    }
+    push (@ret, [$file, $sym, $bind, $ndx ne "UND"]);
+  }
+  close (SYMS) || die ("close $syms_file: $!\n");
+  return @ret;
+}
+
+# Load information about GLOBAL and WEAK symbols defined or used in
+# the standard libraries.
+# Strong symbols (defined or undefined) from a given object.
+%strong_syms = ();
+# Strong undefined symbols from a given object.
+%strong_undef_syms = ();
+# Objects defining a given symbol (strongly or weakly).
+%sym_objs = ();
+@sym_data = list_syms ($libsyms_file);
+foreach my $sym (@sym_data) {
+  my ($file, $name, $bind, $defined) = @$sym;
+  if ($defined) {
+    if (!defined ($sym_objs{$name})) {
+      $sym_objs{$name} = [];
+    }
+    push (@{$sym_objs{$name}}, $file);
+  }
+  if ($bind eq "GLOBAL") {
+    if (!defined ($strong_syms{$file})) {
+      $strong_syms{$file} = [];
+    }
+    push (@{$strong_syms{$file}}, $name);
+    if (!$defined) {
+      if (!defined ($strong_undef_syms{$file})) {
+	$strong_undef_syms{$file} = [];
+      }
+      push (@{$strong_undef_syms{$file}}, $name);
+    }
+  }
+}
+
+# Determine what ELF-level symbols are brought in by use of C-level
+# symbols declared in the given header.
+#
+# The rules followed are heuristic and so may produce false positives
+# and false negatives.
+#
+# * Weak undefined symbols are ignored; however, if a code path that
+# references one (even just to check if its address is 0) is executed,
+# that may conflict with a definition of that symbol in the user's
+# program.
+#
+# * Strong undefined symbols are considered of signficance, but it is
+# possible that (a) any standard library definition is weak, so can be
+# overridden by the user's definition, and (b) the symbol is only used
+# conditionally and not if the program is limited to standard
+# functionality.  (matherr is an example of such a false positive.)
+#
+# * For strong undefined symbols, all possible definitions are
+# considered, rather than being restricted to libraries that are
+# relevant to the given standard (e.g. not considering any libpthread
+# definitions of ISO C symbols).
+#
+# * If a symbol reference is only brought in by the user using a data
+# symbol rather than a function from the standard library, this will
+# not be detected.
+#
+# * If a symbol reference is only brought in by crt*.o or libgcc, this
+# will not be detected.
+#
+# * If a symbol reference is only brought in through __builtin_foo in
+# a standard macro being compiled to call foo, this will not be
+# detected.
+#
+# * Header inclusions should be compiled several times with different
+# options such as -O2, -D_FORTIFY_SOURCE and -D_FILE_OFFSET_BITS=64 to
+# find out what symbols are undefined from such a compilation; this is
+# not yet implemented.
+#
+# * This script finds symbols referenced through use of macros on the
+# basis that if a macro calls an internal function, that function must
+# also be declared in the header.  However, the header might also
+# declare implementation-namespace functions that are not called by
+# any standard macro in the header, resulting in false positives for
+# any symbols brought in only through use of those
+# implementation-namespace functions.
+#
+# * Namespace issues can apply for dynamic linking as well as static
+# linking, when a call is from one shared library to another or uses a
+# PLT entry for a call within a shared library; such issues are only
+# detected by this script if the same namespace issue applies for
+# static linking.
+
+@c_syms = list_exported_functions ("$CC $flags", $standard, $header, $tmpdir);
+$cincfile = "$tmpdir/undef-$$.c";
+$cincfile_o = "$tmpdir/undef-$$.o";
+$cincfile_sym = "$tmpdir/undef-$$.sym";
+open (CINCFILE, ">$cincfile") || die ("open $cincfile: $!\n");
+print CINCFILE "#include <$header>\n";
+foreach my $sym (sort @c_syms) {
+  print CINCFILE "void *__glibc_test_$sym = (void *) &$sym;\n";
+}
+close CINCFILE || die ("close $cincfile: $!\n");
+system ("$CC $flags -D_ISOMAC $CFLAGS{$standard} -c $cincfile -o $cincfile_o")
+  && die ("compiling failed\n");
+system ("LC_ALL=C $READELF -W -s $cincfile_o > $cincfile_sym")
+  && die ("readelf failed\n");
+@elf_syms = list_syms ($cincfile_sym);
+unlink ($cincfile) || die ("unlink $cincfile: $!\n");
+unlink ($cincfile_o) || die ("unlink $cincfile_o: $!\n");
+unlink ($cincfile_sym) || die ("unlink $cincfile_sym: $!\n");
+
+%strong_seen = ();
+%files_seen = ();
+%all_undef = ();
+%current_undef = ();
+foreach my $sym (@elf_syms) {
+  my ($file, $name, $bind, $defined) = @$sym;
+  if ($bind eq "GLOBAL" && !$defined) {
+    $strong_seen{$name} = "[initial] $name";
+    $all_undef{$name} = "[initial] $name";
+    $current_undef{$name} = "[initial] $name";
+  }
+}
+
+while (%current_undef) {
+  %new_undef = ();
+  foreach my $sym (sort keys %current_undef) {
+    foreach my $file (@{$sym_objs{$sym}}) {
+      if (defined ($files_seen{$file})) {
+	next;
+      }
+      $files_seen{$file} = 1;
+      foreach my $ssym (@{$strong_syms{$file}}) {
+	if (!defined ($strong_seen{$ssym})) {
+	  $strong_seen{$ssym} = "$current_undef{$sym} -> [$file] $ssym";
+	}
+      }
+      foreach my $usym (@{$strong_undef_syms{$file}}) {
+	if (!defined ($all_undef{$usym})) {
+	  $all_undef{$usym} = "$current_undef{$sym} -> [$file] $usym";
+	  $new_undef{$usym} = "$current_undef{$sym} -> [$file] $usym";
+	}
+      }
+    }
+  }
+  %current_undef = %new_undef;
+}
+
+$ret = 0;
+foreach my $sym (sort keys %strong_seen) {
+  if ($sym =~ /^_/) {
+    next;
+  }
+  if (defined ($stdsyms{$sym})) {
+    next;
+  }
+  print "$strong_seen{$sym}\n";
+  $ret = 1;
+}
+
+exit $ret;