gh-115119: Fall back to bundled libmpdec if system libmpdec is not found

[erlend-aasland]

$ brew unlink libmpdec $ ./configure --with-system-libmpdec | grep -E "(decimal|mpdec)" checking for --with-system-libmpdec... yes checking for libmpdec >= 2.5.0... no configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled forremovalin Python 3.15) checking for --with-decimal-contextvar... yes checking for decimal libmpdec machine... universal checking for stdlib extension module _decimal... yes $ grep 'DECIMAL_.*FLAGS' Makefile MODULE__DECIMAL_CFLAGS=-I$(srcdir)/Modules/_decimal/libmpdec -DUNIVERSAL=1 MODULE__DECIMAL_LDFLAGS=-lm $(LIBMPDEC_A) $ ./configure | grep -E "(decimal|mpdec)" checking for --with-system-libmpdec... yes checking for libmpdec >= 2.5.0... no configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled forremovalin Python 3.15) checking for --with-decimal-contextvar... yes checking for decimal libmpdec machine... universal checking for stdlib extension module _decimal... yes $ grep 'DECIMAL_.*FLAGS' Makefile MODULE__DECIMAL_CFLAGS=-I$(srcdir)/Modules/_decimal/libmpdec -DUNIVERSAL=1 MODULE__DECIMAL_LDFLAGS=-lm $(LIBMPDEC_A) $ ./configure --without-system-libmpdec | grep -E "(decimal|mpdec)" checking for --with-system-libmpdec... no configure: WARNING: the bundled copy of libmpdecimal is scheduled forremovalin Python 3.15; consider using a system installed mpdecimal library. checking for --with-decimal-contextvar... yes checking for decimal libmpdec machine... universal checking for stdlib extension module _decimal... yes $ grep ‘DECIMAL_.*FLAGS’ Makefile MODULE__DECIMAL_CFLAGS=-I$(srcdir)/Modules/_decimal/libmpdec -DUNIVERSAL=1 MODULE__DECIMAL_LDFLAGS=-lm $(LIBMPDEC_A) $ brew link libmpdec $ ./configure --with-system-libmpdec | grep -E "(decimal|mpdec)" checking for --with-system-libmpdec... yes checking for libmpdec >= 2.5.0... yes checking for --with-decimal-contextvar... yes checking for stdlib extension module _decimal... yes $ grep ‘DECIMAL_.*FLAGS’ Makefile MODULE__DECIMAL_CFLAGS=-I/opt/homebrew/Cellar/mpdecimal/4.0.0/include MODULE__DECIMAL_LDFLAGS=-L/opt/homebrew/Cellar/mpdecimal/4.0.0/lib -lmpdec -lm

• Issue: Unvendor libmpdec sources #115119

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @erlend-aasland for commit c537d8b 🤖

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

[ned-deily]

LGTM, thanks!

[erlend-aasland]

Thanks for the review, Ned! FTR, the buildbot failures all seem unrelated¹

Footnotes

1. buildbot/PPC64LE Fedora Stable Refleaks PR is another regression I introduced in sqlite3; PR is already up merged 😄 ↩

[erlend-aasland]

I'll wait for Zach to chime in before landing.

[vstinner]

cc @hroncok who had issues with this issue.

[erlend-aasland]

Merging, as per Ned's comment on Discord.

[bedevere-app]

GH-119217 is a backport of this pull request to the 3.13 branch.