build system requires explicit compiler, but should discover it

[grimreaper]

BPO	33483
Nosy	@benjaminp, @grimreaper, @matrixise, @iritkatriel
PRs	bpo-33483: more correctly handle finding the C compiler #6780

^{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 2020-10-16.18:45:11.192>
created_at = <Date 2018-05-13.18:28:54.634>
labels = ['build']
title = 'build system requires explicit compiler, but should discover it'
updated_at = <Date 2020-10-16.18:45:11.183>
user = 'https://github.com/grimreaper'

bugs.python.org fields:

activity = <Date 2020-10-16.18:45:11.183>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2020-10-16.18:45:11.192>
closer = 'benjamin.peterson'
components = ['Build']
creation = <Date 2018-05-13.18:28:54.634>
creator = 'eitan.adler'
dependencies = []
files = []
hgrepos = []
issue_num = 33483
keywords = ['patch']
message_count = 5.0
messages = ['316468', '316569', '316585', '316617', '378733']
nosy_count = 4.0
nosy_names = ['benjamin.peterson', 'eitan.adler', 'matrixise', 'iritkatriel']
pr_nums = ['6780']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue33483'
versions = []

[grimreaper]

configure.ac requires explicit configuration for finding the preferred compiler. This results in a non-native way of configuring the system, and does not actually work on most platforms.

Expected behavior:

CC is used to discover the C compiler; CPP, LD, CXX, etc. are used to discover their appropriate tools

Actual:
--without-gcc or --with-icc must be explicitly passed

[matrixise]

Do you have an example where your patch will work and not the current configure.ac. Thank you.

[grimreaper]

On any system where "gcc" is not the correct compiler to use. If it does not exist, is too old, points to the incorrect compiler, etc.

Concretely I have two such systems:

• on one, "gcc" does not exist
• on the other "gcc" is actually a hardlink to "clang"

[benjaminp]

New changeset 98929b5 by Benjamin Peterson (Eitan Adler) in branch 'master':
bpo-33483: more correctly handle finding the C compiler (GH-6780)
98929b5

[iritkatriel]

This seems complete, can it be closed?