This is the "lazy" option.

It seems like one have to set CFLAGS as gcc, not g++, is used to compile some cpp-files... (It is OK not to set CXXFLAGS, at least on my CentOS 7 install.)

You will get a warning though for some of the compile steps:

cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C [enabled by default]

Thanks @oscargus

export CFLAGS=-std=c++11

worked for me too. I'm on RHEL7 (apparently next year we get RHEL9...)

A small follow-up on this. Although it compiles and looks like it installs correctly there is also another message of interest:

/local/data1/miniconda3/compiler_compat/ld: build/freetype-2.6.1/objs/.libs/libfreetype.a(ftinit.o): plugin needed to handle lto object

and running mpl leads to

ImportError: /local/data1/matplotlib/lib/matplotlib/ft2font.cpython-39-x86_64-linux-gnu.so: undefined symbol: FT_Load_Glyph

Do you get similar behavior @rcomer or does it work for you?

(This is for gcc 4.8.5, but I also have 7.3.1 and there it builds without problem, so back to a working version now...)

@oscargus I don't see that message about the plugin, and I just used the environment to reproduce #24545.

@tacaswell I see this is 2 commits. Should I squash-merge or just commit both or something else?

I'll squash this to one (probably should have done that initially).

We tend to reserve squash-merging for PRs with many commits and a contributor who does not feel comfortable squashing them selves.

Cycling CI because it looked like a few checks had network errors that were likely temporary

You can do that directly in Circle; no need to modify the PR.