Autoconf / AX_PTHREAD related update and cleanup.

* m4/ax_pthread.m4: update to AX_PTHREAD 31, fixing a change
  from AX_PTHREAD 29, which has eventually been regarded as
  a bug (workaround in r14481).
* configure.ac: removed the now unneeded AC_CANONICAL_TARGET;
  updated the corresponding comment.

git-svn-id: https://scm.gforge.inria.fr/anonscm/svn/mpfr/trunk@14578 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 15 insertions, 9 deletions

diff --git a/configure.ac b/configure.ac
index 8e1d89f4d..ff40e5eb1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -34,10 +34,16 @@ dnl some other macros (e.g. AX_PTHREAD 29, committed on 2021-02-19) and
 dnl must be called quite early in order to avoid the following warning:
 dnl   warning: AC_ARG_PROGRAM was called before AC_CANONICAL_TARGET
 dnl (we don't use AC_ARG_PROGRAM explicitly, but again, it is invoked by
-dnl another macro, apparently AM_INIT_AUTOMAKE).
-dnl So we need to call AC_CANONICAL_TARGET here, even if we don't use it.
+dnl another macro, apparently AM_INIT_AUTOMAKE). This has eventually been
+dnl fixed in AX_PTHREAD 31.
+dnl Due to this bug in AX_PTHREAD 29, AC_CANONICAL_HOST was moved here and
+dnl AC_CANONICAL_TARGET was added in r14481. However, it is unlikely that
+dnl we need AC_CANONICAL_TARGET in the future; see the comments at
+dnl   https://github.com/autoconf-archive/autoconf-archive/commit/2567e0ce0f3a11b535c6b527386197fb49ff172b
+dnl (introducing AX_PTHREAD 29). Thus it is probably better to avoid it,
+dnl as it could cause confusion. But let's keep AC_CANONICAL_HOST here,
+dnl since this may be a better place than later.
 AC_CANONICAL_HOST
-AC_CANONICAL_TARGET
 
 dnl Older Automake versions than 1.13 may still be supported, but no longer
 dnl tested, and many things have changed in 1.13. Moreover the INSTALL file
diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4
index e5858e50c..9f35d1391 100644
--- a/m4/ax_pthread.m4
+++ b/m4/ax_pthread.m4
@@ -87,11 +87,11 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 30
+#serial 31
 
 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
 AC_DEFUN([AX_PTHREAD], [
-AC_REQUIRE([AC_CANONICAL_TARGET])
+AC_REQUIRE([AC_CANONICAL_HOST])
 AC_REQUIRE([AC_PROG_CC])
 AC_REQUIRE([AC_PROG_SED])
 AC_LANG_PUSH([C])
@@ -158,7 +158,7 @@ ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --
 # --thread-safe: KAI C++
 # pthread-config: use pthread-config program (for GNU Pth library)
 
-case $target_os in
+case $host_os in
 
         freebsd*)
 
@@ -248,7 +248,7 @@ AS_IF([test "x$ax_pthread_clang" = "xyes"],
 # definitions is, on some systems, a strong hint that pthreads support is
 # correctly enabled
 
-case $target_os in
+case $host_os in
         darwin* | hpux* | linux* | osf* | solaris*)
         ax_pthread_check_macro="_REENTRANT"
         ;;
@@ -450,7 +450,7 @@ if test "x$ax_pthread_ok" = "xyes"; then
         AC_CACHE_CHECK([whether more special flags are required for pthreads],
             [ax_cv_PTHREAD_SPECIAL_FLAGS],
             [ax_cv_PTHREAD_SPECIAL_FLAGS=no
-             case $target_os in
+             case $host_os in
              solaris*)
              ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
              ;;
@@ -480,7 +480,7 @@ if test "x$ax_pthread_ok" = "xyes"; then
 
         # More AIX lossage: compile with *_r variant
         if test "x$GCC" != "xyes"; then
-            case $target_os in
+            case $host_os in
                 aix*)
                 AS_CASE(["x/$CC"],
                     [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6],