[lttng-ust.git] / m4 / ax_sys_weak_alias.m4

# SPDX-FileCopyrightText: 2008 Kevin L. Mitchell <klmitch@mit.edu>
#
# SPDX-License-Identifier: FSFAP
#
# ===========================================================================
#    https://www.gnu.org/software/autoconf-archive/ax_sys_weak_alias.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_SYS_WEAK_ALIAS
#
# DESCRIPTION
#
#   Determines whether weak aliases are supported on the system, and if so,
#   what scheme is used to declare them. Also checks to see if aliases can
#   cross object file boundaries, as some systems don't permit them to.
#
#   Most systems permit something called a "weak alias" or "weak symbol."
#   These aliases permit a library to provide a stub form of a routine
#   defined in another library, thus allowing the first library to operate
#   even if the other library is not linked. This macro will check for
#   support of weak aliases, figure out what schemes are available, and
#   determine some characteristics of the weak alias support -- primarily,
#   whether a weak alias declared in one object file may be referenced from
#   another object file.
#
#   There are four known schemes of declaring weak symbols; each scheme is
#   checked in turn, and the first one found is preferred. Note that only
#   one of the mentioned preprocessor macros will be defined!
#
#   1. Function attributes
#
#   This scheme was first introduced by the GNU C compiler, and attaches
#   attributes to particular functions. It is among the easiest to use, and
#   so is the first one checked. If this scheme is detected, the
#   preprocessor macro HAVE_SYS_WEAK_ALIAS_ATTRIBUTE will be defined to 1.
#   This scheme is used as in the following code fragment:
#
#     void __weakf(int c)
#     {
#       /* Function definition... */
#     }
#
#     void weakf(int c) __attribute__((weak, alias("__weakf")));
#
#   2. #pragma weak
#
#   This scheme is in use by many compilers other than the GNU C compiler.
#   It is also particularly easy to use, and fairly portable -- well, as
#   portable as these things get. If this scheme is detected first, the
#   preprocessor macro HAVE_SYS_WEAK_ALIAS_PRAGMA will be defined to 1. This
#   scheme is used as in the following code fragment:
#
#     extern void weakf(int c);
#     #pragma weak weakf = __weakf
#     void __weakf(int c)
#     {
#       /* Function definition... */
#     }
#
#   3. #pragma _HP_SECONDARY_DEF
#
#   This scheme appears to be in use by the HP compiler. As it is rather
#   specialized, this is one of the last schemes checked. If it is the first
#   one detected, the preprocessor macro HAVE_SYS_WEAK_ALIAS_HPSECONDARY
#   will be defined to 1. This scheme is used as in the following code
#   fragment:
#
#     extern void weakf(int c);
#     #pragma _HP_SECONDARY_DEF __weakf weakf
#     void __weakf(int c)
#     {
#       /* Function definition... */
#     }
#
#   4. #pragma _CRI duplicate
#
#   This scheme appears to be in use by the Cray compiler. As it is rather
#   specialized, it too is one of the last schemes checked. If it is the
#   first one detected, the preprocessor macro
#   HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE will be defined to 1. This scheme is
#   used as in the following code fragment:
#
#     extern void weakf(int c);
#     #pragma _CRI duplicate weakf as __weakf
#     void __weakf(int c)
#     {
#       /* Function definition... */
#     }
#
#   In addition to the preprocessor macros listed above, if any scheme is
#   found, the preprocessor macro HAVE_SYS_WEAK_ALIAS will also be defined
#   to 1.
#
#   Once a weak aliasing scheme has been found, a check will be performed to
#   see if weak aliases are honored across object file boundaries. If they
#   are, the HAVE_SYS_WEAK_ALIAS_CROSSFILE preprocessor macro is defined to
#   1.
#
#   This Autoconf macro also makes two substitutions. The first, WEAK_ALIAS,
#   contains the name of the scheme found (one of "attribute", "pragma",
#   "hpsecondary", or "criduplicate"), or "no" if no weak aliasing scheme
#   was found. The second, WEAK_ALIAS_CROSSFILE, is set to "yes" or "no"
#   depending on whether or not weak aliases may cross object file
#   boundaries.
#
# LICENSE
#
#   Copyright (c) 2008 Kevin L. Mitchell <klmitch@mit.edu>
#
#   Copying and distribution of this file, with or without modification, are
#   permitted in any medium without royalty provided the copyright notice
#   and this notice are preserved. This file is offered as-is, without any
#   warranty.

#serial 8

AU_ALIAS([KLM_SYS_WEAK_ALIAS], [AX_SYS_WEAK_ALIAS])
AC_DEFUN([AX_SYS_WEAK_ALIAS], [
  # starting point: no aliasing scheme yet...
  ax_sys_weak_alias=no

  # Figure out what kind of aliasing may be supported...
  _AX_SYS_WEAK_ALIAS_ATTRIBUTE
  _AX_SYS_WEAK_ALIAS_PRAGMA
  _AX_SYS_WEAK_ALIAS_HPSECONDARY
  _AX_SYS_WEAK_ALIAS_CRIDUPLICATE

  # Do we actually support aliasing?
  AC_CACHE_CHECK([how to create weak aliases with $CC],
                 [ax_cv_sys_weak_alias],
                 [ax_cv_sys_weak_alias=$ax_sys_weak_alias])

  # OK, set a #define
  AS_IF([test $ax_cv_sys_weak_alias != no], [
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS], 1,
              [Define this if your system can create weak aliases])
  ])

  # Can aliases cross object file boundaries?
  _AX_SYS_WEAK_ALIAS_CROSSFILE

  # OK, remember the results
  AC_SUBST([WEAK_ALIAS], [$ax_cv_sys_weak_alias])
  AC_SUBST([WEAK_ALIAS_CROSSFILE], [$ax_cv_sys_weak_alias_crossfile])
])

AC_DEFUN([_AX_SYS_WEAK_ALIAS_ATTRIBUTE],
[ # Test whether compiler accepts __attribute__ form of weak aliasing
  AC_CACHE_CHECK([whether $CC accepts function __attribute__((weak,alias()))],
  [ax_cv_sys_weak_alias_attribute], [
    # We add -Werror if it's gcc to force an error exit if the weak attribute
    # isn't understood
    AS_IF([test $GCC = yes], [
      save_CFLAGS=$CFLAGS
      CFLAGS=-Werror])

    # Try linking with a weak alias...
    AC_LINK_IFELSE([
      AC_LANG_PROGRAM([
void __weakf(int c) {}
void weakf(int c) __attribute__((weak, alias("__weakf")));],
        [weakf(0)])],
      [ax_cv_sys_weak_alias_attribute=yes],
      [ax_cv_sys_weak_alias_attribute=no])

    # Restore original CFLAGS
    AS_IF([test $GCC = yes], [
      CFLAGS=$save_CFLAGS])
  ])

  # What was the result of the test?
  AS_IF([test $ax_sys_weak_alias = no &&
         test $ax_cv_sys_weak_alias_attribute = yes], [
    ax_sys_weak_alias=attribute
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS_ATTRIBUTE], 1,
              [Define this if weak aliases may be created with __attribute__])
  ])
])

AC_DEFUN([_AX_SYS_WEAK_ALIAS_PRAGMA],
[ # Test whether compiler accepts #pragma form of weak aliasing
  AC_CACHE_CHECK([whether $CC supports @%:@pragma weak],
  [ax_cv_sys_weak_alias_pragma], [

    # Try linking with a weak alias...
    AC_LINK_IFELSE([
      AC_LANG_PROGRAM([
extern void weakf(int c);
@%:@pragma weak weakf = __weakf
void __weakf(int c) {}],
        [weakf(0)])],
      [ax_cv_sys_weak_alias_pragma=yes],
      [ax_cv_sys_weak_alias_pragma=no])
  ])

  # What was the result of the test?
  AS_IF([test $ax_sys_weak_alias = no &&
         test $ax_cv_sys_weak_alias_pragma = yes], [
    ax_sys_weak_alias=pragma
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS_PRAGMA], 1,
              [Define this if weak aliases may be created with @%:@pragma weak])
  ])
])

AC_DEFUN([_AX_SYS_WEAK_ALIAS_HPSECONDARY],
[ # Test whether compiler accepts _HP_SECONDARY_DEF pragma from HP...
  AC_CACHE_CHECK([whether $CC supports @%:@pragma _HP_SECONDARY_DEF],
  [ax_cv_sys_weak_alias_hpsecondary], [

    # Try linking with a weak alias...
    AC_LINK_IFELSE([
      AC_LANG_PROGRAM([
extern void weakf(int c);
@%:@pragma _HP_SECONDARY_DEF __weakf weakf
void __weakf(int c) {}],
        [weakf(0)])],
      [ax_cv_sys_weak_alias_hpsecondary=yes],
      [ax_cv_sys_weak_alias_hpsecondary=no])
  ])

  # What was the result of the test?
  AS_IF([test $ax_sys_weak_alias = no &&
         test $ax_cv_sys_weak_alias_hpsecondary = yes], [
    ax_sys_weak_alias=hpsecondary
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS_HPSECONDARY], 1,
              [Define this if weak aliases may be created with @%:@pragma _HP_SECONDARY_DEF])
  ])
])

AC_DEFUN([_AX_SYS_WEAK_ALIAS_CRIDUPLICATE],
[ # Test whether compiler accepts "_CRI duplicate" pragma from Cray
  AC_CACHE_CHECK([whether $CC supports @%:@pragma _CRI duplicate],
  [ax_cv_sys_weak_alias_criduplicate], [

    # Try linking with a weak alias...
    AC_LINK_IFELSE([
      AC_LANG_PROGRAM([
extern void weakf(int c);
@%:@pragma _CRI duplicate weakf as __weakf
void __weakf(int c) {}],
        [weakf(0)])],
      [ax_cv_sys_weak_alias_criduplicate=yes],
      [ax_cv_sys_weak_alias_criduplicate=no])
  ])

  # What was the result of the test?
  AS_IF([test $ax_sys_weak_alias = no &&
         test $ax_cv_sys_weak_alias_criduplicate = yes], [
    ax_sys_weak_alias=criduplicate
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE], 1,
              [Define this if weak aliases may be created with @%:@pragma _CRI duplicate])
  ])
])

dnl Note: This macro is modeled closely on AC_LINK_IFELSE, and in fact
dnl depends on some implementation details of that macro, particularly
dnl its use of _AC_MSG_LOG_CONFTEST to log the failed test program and
dnl its use of ac_link for running the linker.
AC_DEFUN([_AX_SYS_WEAK_ALIAS_CROSSFILE],
[ # Check to see if weak aliases can cross object file boundaries
  AC_CACHE_CHECK([whether $CC supports weak aliases across object file boundaries],
  [ax_cv_sys_weak_alias_crossfile], [
    AS_IF([test $ax_cv_sys_weak_alias = no],
          [ax_cv_sys_weak_alias_crossfile=no], [
dnl Must build our own test files...
      # conftest1 contains our weak alias definition...
      cat >conftest1.$ac_ext <<_ACEOF
/* confdefs.h.  */
_ACEOF
      cat confdefs.h >>conftest1.$ac_ext
      cat >>conftest1.$ac_ext <<_ACEOF
/* end confdefs.h.  */

@%:@ifndef HAVE_SYS_WEAK_ALIAS_ATTRIBUTE
extern void weakf(int c);
@%:@endif
@%:@if defined(HAVE_SYS_WEAK_ALIAS_PRAGMA)
@%:@pragma weak weakf = __weakf
@%:@elif defined(HAVE_SYS_WEAK_ALIAS_HPSECONDARY)
@%:@pragma _HP_SECONDARY_DEF __weakf weakf
@%:@elif defined(HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE)
@%:@pragma _CRI duplicate weakf as __weakf
@%:@endif
void __weakf(int c) {}
@%:@ifdef HAVE_SYS_WEAK_ALIAS_ATTRIBUTE
void weakf(int c) __attribute((weak, alias("__weakf")));
@%:@endif
_ACEOF
      # And conftest2 contains our main routine that calls it
      cat >conftest2.$ac_ext <<_ACEOF
/* confdefs.h.  */
_ACEOF
      cat confdefs.h >> conftest2.$ac_ext
      cat >>conftest2.$ac_ext <<_ACEOF
/* end confdefs.h.  */

extern void weakf(int c);
int
main ()
{
  weakf(0);
  return 0;
}
_ACEOF
      # We must remove the object files (if any) ourselves...
      rm -f conftest2.$ac_objext conftest$ac_exeext

      # Change ac_link to compile *2* files together
      save_aclink=$ac_link
      ac_link=`echo "$ac_link" | \
               sed -e 's/conftest\(\.\$ac_ext\)/conftest1\1 conftest2\1/'`
dnl Substitute our own routine for logging the conftest
m4_pushdef([_AC_MSG_LOG_CONFTEST],
[echo "$as_me: failed program was:" >&AS_MESSAGE_LOG_FD
echo ">>> conftest1.$ac_ext" >&AS_MESSAGE_LOG_FD
sed "s/^/| /" conftest1.$ac_ext >&AS_MESSAGE_LOG_FD
echo ">>> conftest2.$ac_ext" >&AS_MESSAGE_LOG_FD
sed "s/^/| /" conftest2.$ac_ext >&AS_MESSAGE_LOG_FD
])dnl
      # Since we created the files ourselves, don't use SOURCE argument
      AC_LINK_IFELSE(, [ax_cv_sys_weak_alias_crossfile=yes],
                     [ax_cv_sys_weak_alias_crossfile=no])
dnl Restore _AC_MSG_LOG_CONFTEST
m4_popdef([_AC_MSG_LOG_CONFTEST])dnl
      # Restore ac_link
      ac_link=$save_aclink

      # We must remove the object files (if any) and C files ourselves...
      rm -f conftest1.$ac_ext conftest2.$ac_ext \
            conftest1.$ac_objext conftest2.$ac_objext
    ])
  ])

  # What were the results of the test?
  AS_IF([test $ax_cv_sys_weak_alias_crossfile = yes], [
    AC_DEFINE([HAVE_SYS_WEAK_ALIAS_CROSSFILE], 1,
              [Define this if weak aliases in other files are honored])
  ])
])
Commit	Line	Data
e03d7c66 MJ	1	# SPDX-FileCopyrightText: 2008 Kevin L. Mitchell <klmitch@mit.edu>
	2	#
	3	# SPDX-License-Identifier: FSFAP
	4	#
f1d4b810	5	# ===========================================================================
e465639e	6	# https://www.gnu.org/software/autoconf-archive/ax_sys_weak_alias.html
f1d4b810 CB	7	# ===========================================================================
	8	#
	9	# SYNOPSIS
	10	#
	11	# AX_SYS_WEAK_ALIAS
	12	#
	13	# DESCRIPTION
	14	#
	15	# Determines whether weak aliases are supported on the system, and if so,
	16	# what scheme is used to declare them. Also checks to see if aliases can
	17	# cross object file boundaries, as some systems don't permit them to.
	18	#
	19	# Most systems permit something called a "weak alias" or "weak symbol."
	20	# These aliases permit a library to provide a stub form of a routine
	21	# defined in another library, thus allowing the first library to operate
	22	# even if the other library is not linked. This macro will check for
	23	# support of weak aliases, figure out what schemes are available, and
	24	# determine some characteristics of the weak alias support -- primarily,
	25	# whether a weak alias declared in one object file may be referenced from
	26	# another object file.
	27	#
	28	# There are four known schemes of declaring weak symbols; each scheme is
e465639e MJ	29	# checked in turn, and the first one found is preferred. Note that only
e465639e MJ	30	# one of the mentioned preprocessor macros will be defined!
f1d4b810 CB	31	#
	32	# 1. Function attributes
	33	#
	34	# This scheme was first introduced by the GNU C compiler, and attaches
	35	# attributes to particular functions. It is among the easiest to use, and
	36	# so is the first one checked. If this scheme is detected, the
	37	# preprocessor macro HAVE_SYS_WEAK_ALIAS_ATTRIBUTE will be defined to 1.
	38	# This scheme is used as in the following code fragment:
	39	#
	40	# void __weakf(int c)
	41	# {
	42	# /* Function definition... */
	43	# }
	44	#
	45	# void weakf(int c) __attribute__((weak, alias("__weakf")));
	46	#
	47	# 2. #pragma weak
	48	#
	49	# This scheme is in use by many compilers other than the GNU C compiler.
	50	# It is also particularly easy to use, and fairly portable -- well, as
	51	# portable as these things get. If this scheme is detected first, the
	52	# preprocessor macro HAVE_SYS_WEAK_ALIAS_PRAGMA will be defined to 1. This
	53	# scheme is used as in the following code fragment:
	54	#
	55	# extern void weakf(int c);
	56	# #pragma weak weakf = __weakf
	57	# void __weakf(int c)
	58	# {
	59	# /* Function definition... */
	60	# }
	61	#
	62	# 3. #pragma _HP_SECONDARY_DEF
	63	#
	64	# This scheme appears to be in use by the HP compiler. As it is rather
	65	# specialized, this is one of the last schemes checked. If it is the first
	66	# one detected, the preprocessor macro HAVE_SYS_WEAK_ALIAS_HPSECONDARY
	67	# will be defined to 1. This scheme is used as in the following code
	68	# fragment:
	69	#
	70	# extern void weakf(int c);
	71	# #pragma _HP_SECONDARY_DEF __weakf weakf
	72	# void __weakf(int c)
	73	# {
	74	# /* Function definition... */
	75	# }
	76	#
	77	# 4. #pragma _CRI duplicate
	78	#
	79	# This scheme appears to be in use by the Cray compiler. As it is rather
	80	# specialized, it too is one of the last schemes checked. If it is the
	81	# first one detected, the preprocessor macro
	82	# HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE will be defined to 1. This scheme is
	83	# used as in the following code fragment:
	84	#
	85	# extern void weakf(int c);
	86	# #pragma _CRI duplicate weakf as __weakf
	87	# void __weakf(int c)
	88	# {
	89	# /* Function definition... */
	90	# }
	91	#
	92	# In addition to the preprocessor macros listed above, if any scheme is
	93	# found, the preprocessor macro HAVE_SYS_WEAK_ALIAS will also be defined
	94	# to 1.
95	#
96	# Once a weak aliasing scheme has been found, a check will be performed to
97	# see if weak aliases are honored across object file boundaries. If they
98	# are, the HAVE_SYS_WEAK_ALIAS_CROSSFILE preprocessor macro is defined to
99	# 1.
100	#
101	# This Autoconf macro also makes two substitutions. The first, WEAK_ALIAS,
102	# contains the name of the scheme found (one of "attribute", "pragma",
103	# "hpsecondary", or "criduplicate"), or "no" if no weak aliasing scheme
104	# was found. The second, WEAK_ALIAS_CROSSFILE, is set to "yes" or "no"
105	# depending on whether or not weak aliases may cross object file
106	# boundaries.
107	#
108	# LICENSE
109	#
110	# Copyright (c) 2008 Kevin L. Mitchell <klmitch@mit.edu>
111	#
112	# Copying and distribution of this file, with or without modification, are
113	# permitted in any medium without royalty provided the copyright notice
114	# and this notice are preserved. This file is offered as-is, without any
115	# warranty.
116
e465639e	117	#serial 8
f1d4b810 CB	118
	119	AU_ALIAS([KLM_SYS_WEAK_ALIAS], [AX_SYS_WEAK_ALIAS])
	120	AC_DEFUN([AX_SYS_WEAK_ALIAS], [
	121	# starting point: no aliasing scheme yet...
	122	ax_sys_weak_alias=no
	123
	124	# Figure out what kind of aliasing may be supported...
	125	_AX_SYS_WEAK_ALIAS_ATTRIBUTE
	126	_AX_SYS_WEAK_ALIAS_PRAGMA
	127	_AX_SYS_WEAK_ALIAS_HPSECONDARY
	128	_AX_SYS_WEAK_ALIAS_CRIDUPLICATE
	129
	130	# Do we actually support aliasing?
	131	AC_CACHE_CHECK([how to create weak aliases with $CC],
	132	[ax_cv_sys_weak_alias],
	133	[ax_cv_sys_weak_alias=$ax_sys_weak_alias])
	134
	135	# OK, set a #define
	136	AS_IF([test $ax_cv_sys_weak_alias != no], [
	137	AC_DEFINE([HAVE_SYS_WEAK_ALIAS], 1,
	138	[Define this if your system can create weak aliases])
	139	])
	140
	141	# Can aliases cross object file boundaries?
	142	_AX_SYS_WEAK_ALIAS_CROSSFILE
	143
	144	# OK, remember the results
	145	AC_SUBST([WEAK_ALIAS], [$ax_cv_sys_weak_alias])
	146	AC_SUBST([WEAK_ALIAS_CROSSFILE], [$ax_cv_sys_weak_alias_crossfile])
	147	])
	148
	149	AC_DEFUN([_AX_SYS_WEAK_ALIAS_ATTRIBUTE],
	150	[ # Test whether compiler accepts __attribute__ form of weak aliasing
	151	AC_CACHE_CHECK([whether $CC accepts function __attribute__((weak,alias()))],
	152	[ax_cv_sys_weak_alias_attribute], [
	153	# We add -Werror if it's gcc to force an error exit if the weak attribute
	154	# isn't understood
	155	AS_IF([test $GCC = yes], [
	156	save_CFLAGS=$CFLAGS
	157	CFLAGS=-Werror])
	158
	159	# Try linking with a weak alias...
	160	AC_LINK_IFELSE([
	161	AC_LANG_PROGRAM([
	162	void __weakf(int c) {}
	163	void weakf(int c) __attribute__((weak, alias("__weakf")));],
	164	[weakf(0)])],
	165	[ax_cv_sys_weak_alias_attribute=yes],
	166	[ax_cv_sys_weak_alias_attribute=no])
	167
	168	# Restore original CFLAGS
	169	AS_IF([test $GCC = yes], [
	170	CFLAGS=$save_CFLAGS])
	171	])
	172
	173	# What was the result of the test?
	174	AS_IF([test $ax_sys_weak_alias = no &&
	175	test $ax_cv_sys_weak_alias_attribute = yes], [
	176	ax_sys_weak_alias=attribute
	177	AC_DEFINE([HAVE_SYS_WEAK_ALIAS_ATTRIBUTE], 1,
	178	[Define this if weak aliases may be created with __attribute__])
	179	])
	180	])
	181
182	AC_DEFUN([_AX_SYS_WEAK_ALIAS_PRAGMA],
183	[ # Test whether compiler accepts #pragma form of weak aliasing
184	AC_CACHE_CHECK([whether $CC supports @%:@pragma weak],
185	[ax_cv_sys_weak_alias_pragma], [
186
187	# Try linking with a weak alias...
188	AC_LINK_IFELSE([
189	AC_LANG_PROGRAM([
190	extern void weakf(int c);
191	@%:@pragma weak weakf = __weakf
192	void __weakf(int c) {}],
193	[weakf(0)])],
194	[ax_cv_sys_weak_alias_pragma=yes],
195	[ax_cv_sys_weak_alias_pragma=no])
196	])
197
198	# What was the result of the test?
199	AS_IF([test $ax_sys_weak_alias = no &&
200	test $ax_cv_sys_weak_alias_pragma = yes], [
201	ax_sys_weak_alias=pragma
202	AC_DEFINE([HAVE_SYS_WEAK_ALIAS_PRAGMA], 1,
203	[Define this if weak aliases may be created with @%:@pragma weak])
204	])
205	])
206
207	AC_DEFUN([_AX_SYS_WEAK_ALIAS_HPSECONDARY],
208	[ # Test whether compiler accepts _HP_SECONDARY_DEF pragma from HP...
209	AC_CACHE_CHECK([whether $CC supports @%:@pragma _HP_SECONDARY_DEF],
210	[ax_cv_sys_weak_alias_hpsecondary], [
211
212	# Try linking with a weak alias...
213	AC_LINK_IFELSE([
214	AC_LANG_PROGRAM([
215	extern void weakf(int c);
216	@%:@pragma _HP_SECONDARY_DEF __weakf weakf
217	void __weakf(int c) {}],
218	[weakf(0)])],
219	[ax_cv_sys_weak_alias_hpsecondary=yes],
220	[ax_cv_sys_weak_alias_hpsecondary=no])
221	])
222
223	# What was the result of the test?
224	AS_IF([test $ax_sys_weak_alias = no &&
225	test $ax_cv_sys_weak_alias_hpsecondary = yes], [
226	ax_sys_weak_alias=hpsecondary
227	AC_DEFINE([HAVE_SYS_WEAK_ALIAS_HPSECONDARY], 1,
228	[Define this if weak aliases may be created with @%:@pragma _HP_SECONDARY_DEF])
229	])
230	])
231
232	AC_DEFUN([_AX_SYS_WEAK_ALIAS_CRIDUPLICATE],
233	[ # Test whether compiler accepts "_CRI duplicate" pragma from Cray
234	AC_CACHE_CHECK([whether $CC supports @%:@pragma _CRI duplicate],
235	[ax_cv_sys_weak_alias_criduplicate], [
236
237	# Try linking with a weak alias...
238	AC_LINK_IFELSE([
239	AC_LANG_PROGRAM([
240	extern void weakf(int c);
241	@%:@pragma _CRI duplicate weakf as __weakf
242	void __weakf(int c) {}],
243	[weakf(0)])],
244	[ax_cv_sys_weak_alias_criduplicate=yes],
245	[ax_cv_sys_weak_alias_criduplicate=no])
246	])
247
248	# What was the result of the test?
249	AS_IF([test $ax_sys_weak_alias = no &&
250	test $ax_cv_sys_weak_alias_criduplicate = yes], [
251	ax_sys_weak_alias=criduplicate
252	AC_DEFINE([HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE], 1,
253	[Define this if weak aliases may be created with @%:@pragma _CRI duplicate])
254	])
255	])
256
257	dnl Note: This macro is modeled closely on AC_LINK_IFELSE, and in fact
258	dnl depends on some implementation details of that macro, particularly
259	dnl its use of _AC_MSG_LOG_CONFTEST to log the failed test program and
260	dnl its use of ac_link for running the linker.
261	AC_DEFUN([_AX_SYS_WEAK_ALIAS_CROSSFILE],
262	[ # Check to see if weak aliases can cross object file boundaries
263	AC_CACHE_CHECK([whether $CC supports weak aliases across object file boundaries],
264	[ax_cv_sys_weak_alias_crossfile], [
265	AS_IF([test $ax_cv_sys_weak_alias = no],
266	[ax_cv_sys_weak_alias_crossfile=no], [
267	dnl Must build our own test files...
268	# conftest1 contains our weak alias definition...
269	cat >conftest1.$ac_ext <<_ACEOF
270	/* confdefs.h. */
271	_ACEOF
272	cat confdefs.h >>conftest1.$ac_ext
273	cat >>conftest1.$ac_ext <<_ACEOF
274	/* end confdefs.h. */
275
276	@%:@ifndef HAVE_SYS_WEAK_ALIAS_ATTRIBUTE
277	extern void weakf(int c);
278	@%:@endif
279	@%:@if defined(HAVE_SYS_WEAK_ALIAS_PRAGMA)
280	@%:@pragma weak weakf = __weakf
281	@%:@elif defined(HAVE_SYS_WEAK_ALIAS_HPSECONDARY)
282	@%:@pragma _HP_SECONDARY_DEF __weakf weakf
283	@%:@elif defined(HAVE_SYS_WEAK_ALIAS_CRIDUPLICATE)
284	@%:@pragma _CRI duplicate weakf as __weakf
285	@%:@endif
286	void __weakf(int c) {}
287	@%:@ifdef HAVE_SYS_WEAK_ALIAS_ATTRIBUTE
288	void weakf(int c) __attribute((weak, alias("__weakf")));
289	@%:@endif
290	_ACEOF
291	# And conftest2 contains our main routine that calls it
292	cat >conftest2.$ac_ext <<_ACEOF
293	/* confdefs.h. */
294	_ACEOF
295	cat confdefs.h >> conftest2.$ac_ext
296	cat >>conftest2.$ac_ext <<_ACEOF
297	/* end confdefs.h. */
298
299	extern void weakf(int c);
300	int
301	main ()
302	{
303	weakf(0);
304	return 0;
305	}
306	_ACEOF
307	# We must remove the object files (if any) ourselves...
308	rm -f conftest2.$ac_objext conftest$ac_exeext
309
310	# Change ac_link to compile 2 files together
311	save_aclink=$ac_link
312	ac_link=`echo "$ac_link" \| \
313	sed -e 's/conftest\(\.\$ac_ext\)/conftest1\1 conftest2\1/'`
314	dnl Substitute our own routine for logging the conftest
315	m4_pushdef([_AC_MSG_LOG_CONFTEST],
316	[echo "$as_me: failed program was:" >&AS_MESSAGE_LOG_FD
317	echo ">>> conftest1.$ac_ext" >&AS_MESSAGE_LOG_FD
318	sed "s/^/\| /" conftest1.$ac_ext >&AS_MESSAGE_LOG_FD
319	echo ">>> conftest2.$ac_ext" >&AS_MESSAGE_LOG_FD
320	sed "s/^/\| /" conftest2.$ac_ext >&AS_MESSAGE_LOG_FD
321	])dnl
322	# Since we created the files ourselves, don't use SOURCE argument
323	AC_LINK_IFELSE(, [ax_cv_sys_weak_alias_crossfile=yes],
324	[ax_cv_sys_weak_alias_crossfile=no])
325	dnl Restore _AC_MSG_LOG_CONFTEST
326	m4_popdef([_AC_MSG_LOG_CONFTEST])dnl
327	# Restore ac_link
328	ac_link=$save_aclink
329
330	# We must remove the object files (if any) and C files ourselves...
331	rm -f conftest1.$ac_ext conftest2.$ac_ext \
332	conftest1.$ac_objext conftest2.$ac_objext
333	])
334	])
335
336	# What were the results of the test?
337	AS_IF([test $ax_cv_sys_weak_alias_crossfile = yes], [
338	AC_DEFINE([HAVE_SYS_WEAK_ALIAS_CROSSFILE], 1,
339	[Define this if weak aliases in other files are honored])
340	])
341	])