Missing definition in configure.ac causing autoreconf to create damaged configure script

[congma]

BPO	43617
Nosy	@vstinner, @tiran, @eli-schwartz, @congma
PRs	bpo-43617: Check autoconf-archive package in configure.ac (GH-25016) #25016 [3.9] bpo-43617: Check autoconf-archive package in configure.ac (GH-25016) (GH-25034) #25034 [3.8] bpo-43617: Check autoconf-archive package in configure.ac (GH-25016) (GH-25035) #25035
Files	0001-configure-use-m4-forbidden-patterns-to-ensure-autore.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-03-27.21:48:36.188>
created_at = <Date 2021-03-24.14:52:18.322>
labels = ['build', '3.8', '3.9', '3.10']
title = 'Missing definition in configure.ac causing autoreconf to create damaged configure script'
updated_at = <Date 2021-04-11.22:23:03.317>
user = 'https://github.com/congma'

bugs.python.org fields:

activity = <Date 2021-04-11.22:23:03.317>
actor = 'eschwartz'
assignee = 'none'
closed = True
closed_date = <Date 2021-03-27.21:48:36.188>
closer = 'christian.heimes'
components = ['Build']
creation = <Date 2021-03-24.14:52:18.322>
creator = 'congma'
dependencies = []
files = ['49954']
hgrepos = []
issue_num = 43617
keywords = ['patch']
message_count = 11.0
messages = ['389463', '389465', '389466', '389467', '389472', '389481', '389600', '389619', '389620', '389622', '390803']
nosy_count = 4.0
nosy_names = ['vstinner', 'christian.heimes', 'eschwartz', 'congma']
pr_nums = ['25016', '25034', '25035']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue43617'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[congma]

The problem
-----------

In the repository, the definition for AX_CHECK_COMPILE_FLAG in Python's configure.ac file is missing. If autoreconf is run, an invalid configure script is generated. The following is the behaviour of running autoreconf followed by configure:

# In cpython repository top-level directory
$ autoreconf
$ mkdir build
$ cd build
$ ../configure  # <- using newly generated configure script
[... omitted ...]
checking for --enable-optimizations... no
../configure: line 6498: syntax error near unexpected token `-fno-semantic-interposition,'
../configure: line 6498: `      AX_CHECK_COMPILE_FLAG(-fno-semantic-interposition,'

The solution
------------

It appears a file was missing in the m4/ directory. The file matches this one from the Autoconf Archive:

https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html

Simply adding the correct m4 file to m4/ should make autoreconf work.

[vstinner]

If autoreconf is run, ...

I never used autoreconf. If you don't run it, ./configure works fine.

I only use "autoconf" and "autoheader".

$ ./configure --enable-optimizations --enable-shared
(...)
$ grep semantic Makefile
CONFIGURE_CFLAGS_NODIST= -fno-semantic-interposition -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -fvisibility=hidden
CONFIGURE_LDFLAGS_NODIST= -fno-semantic-interposition

[congma]

From the configure.ac file:

dnl ***********************************************
dnl * Please run autoreconf to test your changes! *
dnl ***********************************************

I take it to mean "if configure.ac is changed, run autoreconf first", and that's what I did. Could you let me know what is the intended way to modify configure.ac and have it take effect?

[vstinner]

Ah, maybe the configure.ac comment should be updated to suggest running "autoconf" instead ;-)

[tiran]

The extra macros are provided by optional packages. On Fedora and Debian/Ubuntu the package is called autoconf-archive.

[congma]

The extra macros are provided by optional packages. On Fedora and Debian/Ubuntu the package is called autoconf-archive.

Thank you very much. This (and the patch) is clearing things up for me a lot. At first I thought I was supposed to copy the m4 files over from the autoconf archive into the m4 directory under the repo.

[tiran]

New changeset 5d6e8c1 by Christian Heimes in branch 'master':
bpo-43617: Check autoconf-archive package in configure.ac (GH-25016)
5d6e8c1

[tiran]

New changeset 064bc07 by Christian Heimes in branch '3.9':
[3.9] bpo-43617: Check autoconf-archive package in configure.ac (GH-25016) (GH-25034)
064bc07

[tiran]

New changeset e516290 by Christian Heimes in branch '3.8':
[3.8] bpo-43617: Check autoconf-archive package in configure.ac (GH-25016) (GH-25035)
e516290

[tiran]

Thanks for the bug report! I ran into the issue a couple of weeks ago on one machine that had autoconf but not the archive package installed.

[eli-schwartz]

Hmm, I've seen this accomplished elsewhere using m4_pattern_forbid, which would make autoreconf fail with the following message:

configure.ac:17: error: possibly undefined macro: AX_C_FLOAT_WORDS_BIGENDIAN
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
configure.ac:5586: error: possibly undefined macro: AX_CHECK_OPENSSL
autoreconf: error: /usr/bin/autoconf failed with exit status: 1

Example patch attached.