Dynamic cairo symbol lookup

[lazka]

wip

A test to see if we could load cairo symbols at runtime only when needed, so a pycairo doesn't need to be rebuilt if cairo is rebuilt with a different config.

I've never done something like this, so not sure how portable that all is. With some macro magic we could make it optional if that turns out to be tricky.

[lazka]

The main thing is that statically linking on non-Windows will fail with this, and I wonder if there is a way to detect that automatically.

[stuaxo]

I wonder if this could solve a few issues: One I use case I think is really interesting, is having parallel builds of cairo with different --enable flags (built at the same time).

Another is cairo built in a virtualenv vs in the system.

[lazka]

Yeah, the combination of distros changing something with cairo + cached wheels from previous pycairo installs is one source of conflicts.

[lazka]

The main thing is that statically linking on non-Windows will fail with this, and I wonder if there is a way to detect that automatically.

I doesn't seem there is. So we might have to add an option to disable this in case someone wants to link statically (rare on non-Windows). On Windows we can use CAIRO_WIN32_STATIC_BUILD to detect that case, since the user is required to set that for static linking.

[eli-schwartz]

For example, vim has:

  --enable-luainterp=OPTS      Include Lua interpreter.  default=no OPTS=no/yes/dynamic
  --enable-mzschemeinterp      Include MzScheme interpreter.
  --enable-perlinterp=OPTS     Include Perl interpreter.  default=no OPTS=no/yes/dynamic
  --enable-pythoninterp=OPTS   Include Python interpreter. default=no OPTS=no/yes/dynamic
  --enable-python3interp=OPTS  Include Python3 interpreter. default=no OPTS=no/yes/dynamic
  --enable-tclinterp=OPTS      Include Tcl interpreter. default=no OPTS=no/yes/dynamic
  --enable-rubyinterp=OPTS     Include Ruby interpreter.  default=no OPTS=no/yes/dynamic

You could make it an error to static link while also setting it to dlopen? The distinguishing factor is basically "did the user set -static in LDFLAGS", right? You could check this via a cc.run() check perhaps.