Configure EXEEXT hacks are interfering with AX_C_FLOAT_WORDS_BIGENDIAN

[erlend-aasland]

Bug report

Bug description:

We mess up EXEEXT in configure.ac:

cpython/configure.ac

Lines 1323 to 1340 in cda0ec8

	AC_MSG_CHECKING([for --with-suffix])
	AC_ARG_WITH([suffix],
	[AS_HELP_STRING([--with-suffix=SUFFIX], [set executable suffix to SUFFIX (default is empty, yes is mapped to '.exe')])],
	[
	AS_CASE([$with_suffix],
	[no], [EXEEXT=],
	[yes], [EXEEXT=.exe],
	[EXEEXT=$with_suffix]
	)
	], [
	AS_CASE([$ac_sys_system/$ac_sys_emscripten_target],
	[Emscripten/browser*], [EXEEXT=.js],
	[Emscripten/node*], [EXEEXT=.js],
	[WASI/*], [EXEEXT=.wasm],
	[EXEEXT=]
	)
	])
	AC_MSG_RESULT([$EXEEXT])

This creates problems¹, since AX_C_FLOAT_WORDS_BIGENDIAN expects EXEEXT and ac_exeext to be the same. EXEEXT and ac_exeext are set up by AC_PROG_CC:

cpython/configure.ac

Line 1026 in cda0ec8

AC_PROG_CC

We can mitigate this by:

1. setting ac_exeext=$EXEEXT after L1340 in configure.ac
2. use another variable than EXEEXT; for example EXE_SUFFIX
3. other workarounds?

My gut feel regarding these is that I'd really not like to add more EXEEXT hacks, so I'd like to avoid 1). 2) should be ok, given that no-one else are depending on EXEEXT (cc. @hroncok).

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux, macOS, Other

Linked PRs

• gh-125698: Replace EXEEXT with EXE_SUFFIX #125699
• gh-125698: Restore EXEEXT in configure and Make #125758
• gh-125698: Autoconf: Sync EXEEXT and ac_exeext #125995
• [3.13] gh-125698: Autoconf: Sync EXEEXT and ac_exeext (GH-125995) #126006
• [3.12] gh-125698: Autoconf: Sync EXEEXT and ac_exeext (GH-125995) #126007

Footnotes

1. https://github.com/python/cpython/pull/125571#issuecomment-2422385731, https://github.com/python/cpython/pull/125571#issuecomment-2422414137 ↩

[erlend-aasland]

cc. @damelang, author of AX_C_FLOAT_WORDS_BIGENDIAN.

[erlend-aasland]

Another workaround, could be to move the float checks to before our EXEEXT hacks, but who knows what will break next time.

[hroncok]

cc. @hroncok

I am not entirely sure what's my input here supposed to be.

[erlend-aasland]

I am not entirely sure what's my input here supposed to be.

I just suspected a third-party consumer of our build system would like to receive a heads-up when I proposed a rename of one of the configure/Make variables.

Anyway, as I feared, the renaming broke CI, so I'm reverting it. I suggest instead to amend Dan Amelang's patch to use ac_exeext iso. EXEEXT.

[erlend-aasland]

I amended Dan's patch to use ac_exeext in Codespaces, and can confirm that that approach works for WASI.

[erlend-aasland]

See python/cpython-devcontainers#30 for a proposed patch.

[erlend-aasland]

I amended Dan's patch to use ac_exeext in Codespaces, and can confirm that that approach works for WASI.

OTOH, most of the macros in autoconf-archive does actually use EXEEXT, and not ac_exeext, implying that if we should land python/cpython-devcontainers#30, we'd possibly run into a similar issue with another macro at a later point¹. Perhaps we should just work around this in configure.ac by making sure ac_exeext is set to the same as EXEEXT.

Footnotes

1. yet another reason to switch to a more modern build system ↩

[erlend-aasland]

Landed on the following solution:

• gh-125698: Autoconf: Sync EXEEXT and ac_exeext #125995

Automerge enabled for the backports. Closing this as completed.