Fix: configure: support Autoconf 2.70

The newly-released autoconf 2.70 introduces a number of breaking
changes [1] and is being rolled-out by some distros.

Amongst those changes, the AC_PROG_CC_STDC macro is marked as obsolete
and was merged into AC_PROG_CC, which we already use. On 2.70, this
results in a warning which we handle as an error.

A version check is added to invoke the AC_PROG_CC_STDC macro only when
running a pre-2.70 version of autoconf, fixing the issue.

[1] https://lwn.net/Articles/839395/

[ Backport by Mathieu Desnoyers: removed ax_pthread.m4 bits which are
  not present in stable-2.12 and prior. ]

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I2f4eac788638924aa4960b54374d09de73957925

diff --git a/configure.ac b/configure.ac
index d140b0865fd3d651e74c7b1fa073b4b989697c7c..7f5efdd8576d0001148d0b569ea11e7a5f3f3c29 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -53,7 +53,8 @@ AC_REQUIRE_AUX_FILE([tap-driver.sh])
 AC_USE_SYSTEM_EXTENSIONS
 AC_SYS_LARGEFILE
 AC_PROG_CC
-AC_PROG_CC_STDC
+# AC_PROG_CC_STDC was merged in AC_PROG_CC in autoconf 2.70
+m4_version_prereq([2.70], [], [AC_PROG_CC_STDC])
 AC_PROG_CXX
 RW_PROG_CXX_WORKS
 AM_CONDITIONAL([CXX_WORKS], [test "x$rw_cv_prog_cxx_works" = "xyes"])