regex: avoid glibc deadlock during configure glibc has a known bug where certain corruptions of the heap can cause malloc to default to printing a debug message that includes a backtrace, but the act of getting the backtrace uses dlopen which in turn calls into malloc, causing a recursive lock ending in deadlock. Thus, when configure is probing for a known glibc heap corruption bug, the overall configure would hang. The solution suggested by glibc developers is to force malloc to quit printing debug messages, which avoids recursive malloc. * m4/regex.m4 (gl_REGEX): Avoid recursive malloc deadlock when glibc bug 15078 in turn triggers bug 16159. Reported by Michal Privoznik. Signed-off-by: Eric Blake <eblake@redhat.com>

# getsubopt.m4 serial 5
dnl Copyright (C) 2004, 2007, 2009-2013 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_GETSUBOPT],
[
  dnl Persuade glibc <stdlib.h> to declare getsubopt().
  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])

  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
  AC_CHECK_FUNCS_ONCE([getsubopt])
  if test $ac_cv_func_getsubopt = no; then
    HAVE_GETSUBOPT=0
  fi
])

# Prerequisites of lib/getsubopt.c.
AC_DEFUN([gl_PREREQ_GETSUBOPT], [:])