DOC: add some hints to build, test

[mattip]

Some things I found helpful when trying this out

• document that the tests will run "full" by default, and show how to skip slow tests
• document adding CFLAGS for debugging. The meson FAQ seemed to suggest this is best practices, maybe there is a better way?

[eli-schwartz]

document adding CFLAGS for debugging. The meson FAQ seemed to suggest this is best practices, maybe there is a better way?

These particular flags are really equivalent to passing the meson_args -Dbuildtype=debug.

[mattip]

Does -Dbuildtype=debug require a debug build of python either on linux or windows?

[mattip]

The first point is connected to #40

[eli-schwartz]

Does -Dbuildtype=debug require a debug build of python either on linux or windows?

Definitely not on Linux, since it maps to exactly the combination of -Doptimization=0 -Ddebug=true.

Good point about Windows, since by default the value of b_vscrt is from_buildtype and per the table at https://mesonbuild.com/Builtin-options.html this will map to also setting /MDd.

(I have no idea whether it is compatible with a release build of python itself.)

[mattip]

The problem with /MDd is that it will link to a different runtime library, so it will require a debug build of python for windows. Then this will percolate out to all other c-extension modules, so you must rebuild the entire environment.

I usually set the cflags "/Od /Zi" instead, which is much more like "-O0 -g" for gcc. Well, that is what I tell people I do. In reality, since using a debugger in windows is painful, I first use a lot of debug prints to see if I can avoid using a debugger at all, so then all I care about is having a small failing test and a quick build turn-around.

[stefanv]

Thanks for this, Matti!