Configuring with any autoconf version other then 2.69 fails

[Anonymous Maarten]

Hello,

Running autoreconf, with autoconf 2.71, fails with the following error:

configure.ac:33: error: Please use exactly Autoconf 2.69 instead of 2.71.

The cause are the following lines:

libbacktrace/config/override.m4

Lines 30 to 48 in 4f57c99

 dnl Ensure exactly this Autoconf version is used 
 m4_ifndef([_GCC_AUTOCONF_VERSION], 
   [m4_define([_GCC_AUTOCONF_VERSION], [2.69])]) 
  
 dnl Test for the exact version when AC_INIT is expanded. 
 dnl This allows to update the tree in steps (for testing) 
 dnl by putting 
 dnl   m4_define([_GCC_AUTOCONF_VERSION], [X.Y]) 
 dnl in configure.ac before AC_INIT, 
 dnl without rewriting this file. 
 dnl Or for updating the whole tree at once with the definition above. 
 AC_DEFUN([_GCC_AUTOCONF_VERSION_CHECK], 
 [m4_if(m4_defn([_GCC_AUTOCONF_VERSION]), 
   m4_defn([m4_PACKAGE_VERSION]), [], 
   [m4_fatal([Please use exactly Autoconf ]_GCC_AUTOCONF_VERSION[ instead of ]m4_defn([m4_PACKAGE_VERSION])[.])]) 
 ]) 
 m4_define([AC_INIT], m4_defn([AC_INIT])[ 
 _GCC_AUTOCONF_VERSION_CHECK 
 ]) 

What is the reason only 2.69 is allowed? Does the configure script use undocumented features?
Would it be ok to remove these lines?

[Marian Klymov]

There was similar issue #71 (comment)

[Anonymous Maarten]

Thanks for the link. I'm closing this one.

[Ian Lance Taylor]

I've reconsidered this. While the version of libbacktrace in the GCC sources should require autoconf 2.69, there's no special reason to require 2.69 in the standalone libbacktrace. I've commented out the code (copied from GCC) that requires exactly 2.69.

That said using autoconf 2.71 reports some warnings about obsolete autoconf commands. I don't plan to fix those unless and until GCC starts avoiding them.