1# alloca.m4 serial 14
2dnl Copyright (C) 2002-2004, 2006-2007, 2009-2012 Free Software Foundation,
3dnl Inc.
4dnl This file is free software; the Free Software Foundation
5dnl gives unlimited permission to copy and/or distribute it,
6dnl with or without modifications, as long as this notice is preserved.
7
8AC_DEFUN([gl_FUNC_ALLOCA],
9[
10  AC_REQUIRE([AC_FUNC_ALLOCA])
11  if test $ac_cv_func_alloca_works = no; then
12    gl_PREREQ_ALLOCA
13  fi
14
15  # Define an additional variable used in the Makefile substitution.
16  if test $ac_cv_working_alloca_h = yes; then
17    AC_CACHE_CHECK([for alloca as a compiler built-in], [gl_cv_rpl_alloca], [
18      AC_EGREP_CPP([Need own alloca], [
19#if defined __GNUC__ || defined _AIX || defined _MSC_VER
20        Need own alloca
21#endif
22        ], [gl_cv_rpl_alloca=yes], [gl_cv_rpl_alloca=no])
23    ])
24    if test $gl_cv_rpl_alloca = yes; then
25      dnl OK, alloca can be implemented through a compiler built-in.
26      AC_DEFINE([HAVE_ALLOCA], [1],
27        [Define to 1 if you have 'alloca' after including <alloca.h>,
28         a header that may be supplied by this distribution.])
29      ALLOCA_H=alloca.h
30    else
31      dnl alloca exists as a library function, i.e. it is slow and probably
32      dnl a memory leak. Don't define HAVE_ALLOCA in this case.
33      ALLOCA_H=
34    fi
35  else
36    ALLOCA_H=alloca.h
37  fi
38  AC_SUBST([ALLOCA_H])
39  AM_CONDITIONAL([GL_GENERATE_ALLOCA_H], [test -n "$ALLOCA_H"])
40])
41
42# Prerequisites of lib/alloca.c.
43# STACK_DIRECTION is already handled by AC_FUNC_ALLOCA.
44AC_DEFUN([gl_PREREQ_ALLOCA], [:])
45
46# This works around a bug in autoconf <= 2.68.
47# See <http://lists.gnu.org/archive/html/bug-gnulib/2011-06/msg00277.html>.
48
49m4_version_prereq([2.69], [] ,[
50
51# This is taken from the following Autoconf patch:
52# http://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=6cd9f12520b0d6f76d3230d7565feba1ecf29497
53
54# _AC_LIBOBJ_ALLOCA
55# -----------------
56# Set up the LIBOBJ replacement of 'alloca'.  Well, not exactly
57# AC_LIBOBJ since we actually set the output variable 'ALLOCA'.
58# Nevertheless, for Automake, AC_LIBSOURCES it.
59m4_define([_AC_LIBOBJ_ALLOCA],
60[# The SVR3 libPW and SVR4 libucb both contain incompatible functions
61# that cause trouble.  Some versions do not even contain alloca or
62# contain a buggy version.  If you still want to use their alloca,
63# use ar to extract alloca.o from them instead of compiling alloca.c.
64AC_LIBSOURCES(alloca.c)
65AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl
66AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.])
67
68AC_CACHE_CHECK(whether 'alloca.c' needs Cray hooks, ac_cv_os_cray,
69[AC_EGREP_CPP(webecray,
70[#if defined CRAY && ! defined CRAY2
71webecray
72#else
73wenotbecray
74#endif
75], ac_cv_os_cray=yes, ac_cv_os_cray=no)])
76if test $ac_cv_os_cray = yes; then
77  for ac_func in _getb67 GETB67 getb67; do
78    AC_CHECK_FUNC($ac_func,
79                  [AC_DEFINE_UNQUOTED(CRAY_STACKSEG_END, $ac_func,
80                                      [Define to one of '_getb67', 'GETB67',
81                                       'getb67' for Cray-2 and Cray-YMP
82                                       systems. This function is required for
83                                       'alloca.c' support on those systems.])
84    break])
85  done
86fi
87
88AC_CACHE_CHECK([stack direction for C alloca],
89               [ac_cv_c_stack_direction],
90[AC_RUN_IFELSE([AC_LANG_SOURCE(
91[AC_INCLUDES_DEFAULT
92int
93find_stack_direction (int *addr, int depth)
94{
95  int dir, dummy = 0;
96  if (! addr)
97    addr = &dummy;
98  *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
99  dir = depth ? find_stack_direction (addr, depth - 1) : 0;
100  return dir + dummy;
101}
102
103int
104main (int argc, char **argv)
105{
106  return find_stack_direction (0, argc + !argv + 20) < 0;
107}])],
108               [ac_cv_c_stack_direction=1],
109               [ac_cv_c_stack_direction=-1],
110               [ac_cv_c_stack_direction=0])])
111AH_VERBATIM([STACK_DIRECTION],
112[/* If using the C implementation of alloca, define if you know the
113   direction of stack growth for your system; otherwise it will be
114   automatically deduced at runtime.
115        STACK_DIRECTION > 0 => grows toward higher addresses
116        STACK_DIRECTION < 0 => grows toward lower addresses
117        STACK_DIRECTION = 0 => direction of growth unknown */
118@%:@undef STACK_DIRECTION])dnl
119AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)
120])# _AC_LIBOBJ_ALLOCA
121])
122