bpo-45723: Prepare support for autoconf 2.71 (GH-29441)

[tiran]

AC_PROG_EGREP should be checked explicitly.

AC_CONFIG_HEADER -> AC_CONFIG_HEADERS

AC_USE_SYSTEM_EXTENSIONS must be defined before first use of AC_LINK
or AC_COMPILE macros.

STDC_HEADERS and AC_HEADER_TIME are obsolete.

Signed-off-by: Christian Heimes christian@python.org

https://bugs.python.org/issue45723

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @tiran for commit 2b2a10ebcb4216c271248e2191c64f29a7a68912 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[tiran]

All changes are based on the output of 2.71's autoupdate tool.

[erlend-aasland]

I took a quick look and left some comments.

[tiran]

autoconf 2.71 has deprecated the macro:

configure.ac:660: warning: The macro `AC_PROG_CC_C99' is obsolete. configure.ac:660: You should run autoupdate. 

[erlend-aasland]

autoconf 2.71 has deprecated the macro:

configure.ac:660: warning: The macro `AC_PROG_CC_C99' is obsolete. configure.ac:660: You should run autoupdate. 

Oh, well 😆

[tiran]

In autoconf 2.71, AC_PROG_CC_C99 is an alias for AC_PROG_CC

[erlend-aasland]

In autoconf 2.71, AC_PROG_CC_C99 is an alias for AC_PROG_CC

It seems that we can use AC_PROG_CC and check ac_cv_prog_cc_c99:

Otherwise, if ac_cv_prog_cc_c99 is set to any value other than ‘no’ (including the empty string), then CC can compile code as standard C 1999, and this mode has been enabled 

[erlend-aasland]

BTW, we need to make sure we set CFLAGS before calling AC_PROG_CC, so we don't accidentally default to -g -O2.

[tiran]

In autoconf 2.71, AC_PROG_CC_C99 is an alias for AC_PROG_CC

It seems that we can use AC_PROG_CC and check ac_cv_prog_cc_c99:

Otherwise, if ac_cv_prog_cc_c99 is set to any value other than ‘no’ (including the empty string), then CC can compile code as standard C 1999, and this mode has been enabled 

autoconf 2.71 no longer defines the variable ac_cv_prog_cc_c99. autoconf 2.69 only defines it for AC_PROG_CC_STDC.

[erlend-aasland]

LGTM, but I think one NEWS entry is enough ;)

[tiran]

LGTM, but I think one NEWS entry is enough ;)

Oops :)

I have removed the second entry and rebased the PR.