If a C23 compiler is detected, try asking for C17.
Branches before 16 can't be compiled with a C23 compiler (see
deprecation warnings silenced by commit f9a56e72, and non-back-patchable
changes made in 16 by commit 1c27d16e). Test __STDC_VERSION__, and if
it's above C17 then try appending -std=gnu17. The test is done with the
user's CFLAGS, so an acceptable language version can also be configured
manually that way.
This is done in branches 15 and older, back to 9.2, per policy of
keeping them buildable with modern tools.
Discussion: https://postgr.es/m/87o72eo9iu.fsf%40gentoo.org
Branch
------
REL9_3_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/102be6634e6fe1dec7a78ee4f4ed6a51285682bd
Modified Files
--------------
configure | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
configure.in | 20 ++++++++++
2 files changed, 144 insertions(+)
