Bug report

Bug summary

If matplotlib is build with -fno-lto CFLAGS then the build is completed "successfully" but will fail to import
This was 1st spotted with matplotlib-3.3.0 and did not occur again with later versions until 3.3.3

TEST 1:
CFLAGS="-O2 -pipe -fomit-frame-pointer -march=native"

emerge matplotlibCalculating dependencies... done!>>>Verifying ebuild manifests>>>Emerging (1 of 1) dev-python/matplotlib-3.3.3::gentoo>>>Installing (1 of 1) dev-python/matplotlib-3.3.3::gentoo>>> Jobs: 1 of 1 complete                           Load avg: 0.93, 0.65, 0.92>>>Auto-cleaning packages...

fluidmotion ~ # pythonPython 3.8.7 (default, Dec 22 2020, 17:30:32)[GCC 10.2.0] on linuxType "help", "copyright", "credits" or "license" for more information.>>> import matplotlib>>>

BUILD LOG: dev-python:matplotlib-3.3.3:20210103-123758.log

TEST 2:
CFLAGS="-O2 -pipe -fomit-frame-pointer -march=native -fno-lto"

emerge matplotlibCalculating dependencies... done!>>> Verifying ebuild manifests>>> Emerging (1 of 1) dev-python/matplotlib-3.3.3::gentoo>>> Installing (1 of 1) dev-python/matplotlib-3.3.3::gentoo>>> Jobs: 1 of 1 complete                           Load avg: 0.73, 0.57, 0.84>>> Auto-cleaning packages...

fluidmotion /var/log/portage # pythonPython 3.8.7 (default, Dec 22 2020, 17:30:32)[GCC 10.2.0] on linuxType "help", "copyright", "credits" or "license" for more information.>>> import matplotlibTraceback (most recent call last):  File "<stdin>", line 1, in <module>  File "/usr/lib/python3.8/site-packages/matplotlib/__init__.py", line 174, in <module>    _check_versions()  File "/usr/lib/python3.8/site-packages/matplotlib/__init__.py", line 159, in _check_versions    from . import ft2fontImportError: dynamic module does not define module export function (PyInit_ft2font)>>>

BUILD LOG:dev-python:matplotlib-3.3.3:20210103-124106.log

Difference:
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/checkdep_freetype2.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/checkdep_freetype2.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/ft2font.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/ft2font.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/ft2font_wrapper.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/ft2font_wrapper.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/mplutils.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/mplutils.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/py_converters.o: plugin needed to handle lto object
/var/tmp/portage/dev-python/matplotlib-3.3.3/work/matplotlib-3.3.3-python3_8/build/temp.linux-x86_64-3.8/src/py_converters.o: plugin needed to handle lto object
/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/crtendS.o: plugin needed to handle lto object

RAW build logs can be found here:https://bugs.gentoo.org/736122