# alloca.m4 serial 14

dnl Copyright (C) 2002-2004, 2006-2007, 2009-2018 Free Software Foundation,

dnl 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_ALLOCA],

[

  AC_REQUIRE([AC_FUNC_ALLOCA])

  if test $ac_cv_func_alloca_works = no; then

    gl_PREREQ_ALLOCA

  fi

  # Define an additional variable used in the Makefile substitution.

  if test $ac_cv_working_alloca_h = yes; then

    AC_CACHE_CHECK([for alloca as a compiler built-in], [gl_cv_rpl_alloca], [

      AC_EGREP_CPP([Need own alloca], [

#if defined __GNUC__ || defined _AIX || defined _MSC_VER

        Need own alloca

#endif

        ], [gl_cv_rpl_alloca=yes], [gl_cv_rpl_alloca=no])

    ])

    if test $gl_cv_rpl_alloca = yes; then

      dnl OK, alloca can be implemented through a compiler built-in.

      AC_DEFINE([HAVE_ALLOCA], [1],

        [Define to 1 if you have 'alloca' after including <alloca.h>,

         a header that may be supplied by this distribution.])

      ALLOCA_H=alloca.h

    else

      dnl alloca exists as a library function, i.e. it is slow and probably

      dnl a memory leak. Don't define HAVE_ALLOCA in this case.

      ALLOCA_H=

    fi

  else

    ALLOCA_H=alloca.h

  fi

  AC_SUBST([ALLOCA_H])

  AM_CONDITIONAL([GL_GENERATE_ALLOCA_H], [test -n "$ALLOCA_H"])

])

# Prerequisites of lib/alloca.c.

# STACK_DIRECTION is already handled by AC_FUNC_ALLOCA.

AC_DEFUN([gl_PREREQ_ALLOCA], [:])

# This works around a bug in autoconf <= 2.68.

# See <https://lists.gnu.org/r/bug-gnulib/2011-06/msg00277.html>.

m4_version_prereq([2.69], [] ,[

# This is taken from the following Autoconf patch:

# https://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=6cd9f12520b0d6f76d3230d7565feba1ecf29497

# _AC_LIBOBJ_ALLOCA

# -----------------

# Set up the LIBOBJ replacement of 'alloca'.  Well, not exactly

# AC_LIBOBJ since we actually set the output variable 'ALLOCA'.

# Nevertheless, for Automake, AC_LIBSOURCES it.

m4_define([_AC_LIBOBJ_ALLOCA],

[# The SVR3 libPW and SVR4 libucb both contain incompatible functions

# that cause trouble.  Some versions do not even contain alloca or

# contain a buggy version.  If you still want to use their alloca,

# use ar to extract alloca.o from them instead of compiling alloca.c.

AC_LIBSOURCES(alloca.c)

AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl

AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.])

AC_CACHE_CHECK(whether 'alloca.c' needs Cray hooks, ac_cv_os_cray,

[AC_EGREP_CPP(webecray,

[#if defined CRAY && ! defined CRAY2

webecray

#else

wenotbecray

#endif

], ac_cv_os_cray=yes, ac_cv_os_cray=no)])

if test $ac_cv_os_cray = yes; then

  for ac_func in _getb67 GETB67 getb67; do

    AC_CHECK_FUNC($ac_func,

                  [AC_DEFINE_UNQUOTED(CRAY_STACKSEG_END, $ac_func,

                                      [Define to one of '_getb67', 'GETB67',

                                       'getb67' for Cray-2 and Cray-YMP

                                       systems. This function is required for

                                       'alloca.c' support on those systems.])

    break])

  done

fi

AC_CACHE_CHECK([stack direction for C alloca],

               [ac_cv_c_stack_direction],

[AC_RUN_IFELSE([AC_LANG_SOURCE(

[AC_INCLUDES_DEFAULT

int

find_stack_direction (int *addr, int depth)

{

  int dir, dummy = 0;

  if (! addr)

    addr = &dummy;

  *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;

  dir = depth ? find_stack_direction (addr, depth - 1) : 0;

  return dir + dummy;

}

int

main (int argc, char **argv)

{

  return find_stack_direction (0, argc + !argv + 20) < 0;

}])],

               [ac_cv_c_stack_direction=1],

               [ac_cv_c_stack_direction=-1],

               [ac_cv_c_stack_direction=0])])

AH_VERBATIM([STACK_DIRECTION],

[/* If using the C implementation of alloca, define if you know the

   direction of stack growth for your system; otherwise it will be

   automatically deduced at runtime.

        STACK_DIRECTION > 0 => grows toward higher addresses

        STACK_DIRECTION < 0 => grows toward lower addresses

        STACK_DIRECTION = 0 => direction of growth unknown */

@%:@undef STACK_DIRECTION])dnl

AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)

])# _AC_LIBOBJ_ALLOCA

])