BLD: enable building NumPy with Meson

This enables building with NumPy on Linux and macOS. Windows support
should be complete to, but is untested as of now and may need a few
tweaks. This contains:
- A set of `meson.build` files and related code generation script
  tweaks, header templates, etc.
- One CI job on Linux
- Basic docs on using Meson to build NumPy (not yet integrated in the
  html docs, it's too early for that - this is for early adopters right
  now).

The build should be complete, with the major exception of SIMD support.
The full test suite passes. See gh-22546 for the tracking issue with
detailed notes on the plan for switching NumPy to Meson as its build
system.

Co-authored-by: Stefan van der Walt <stefanv@berkeley.edu>

2 files changed, 37 insertions, 32 deletions

diff --git a/doc/source/f2py/code/meson.build b/doc/source/f2py/code/meson.build
index 04276a176..1d409f2fb 100644
--- a/doc/source/f2py/code/meson.build
+++ b/doc/source/f2py/code/meson.build
@@ -1,31 +1,35 @@
 project('f2py_examples', 'c',
   version : '0.1',
-  default_options : ['warning_level=2'])
+  license: 'BSD-3',
+  meson_version: '>=0.64.0',
+  default_options : ['warning_level=2'],
+)
 
 add_languages('fortran')
 
 py_mod = import('python')
-py3 = py_mod.find_installation('python3')
-py3_dep = py3.dependency()
-message(py3.path())
-message(py3.get_install_dir())
+py = py_mod.find_installation(pure: false)
+py_dep = py.dependency()
 
-incdir_numpy = run_command(py3,
+incdir_numpy = run_command(py,
   ['-c', 'import os; os.chdir(".."); import numpy; print(numpy.get_include())'],
   check : true
 ).stdout().strip()
 
-incdir_f2py = run_command(py3,
+incdir_f2py = run_command(py,
     ['-c', 'import os; os.chdir(".."); import numpy.f2py; print(numpy.f2py.get_include())'],
     check : true
 ).stdout().strip()
 
 inc_np = include_directories(incdir_numpy, incdir_f2py)
 
-py3.extension_module('fib2',
-           'fib1.f',
-           'fib2module.c',
-           incdir_f2py+'/fortranobject.c',
-           include_directories: inc_np,
-           dependencies : py3_dep,
-           install : true)
\ No newline at end of file
+py.extension_module('fib2',
+  [
+    'fib1.f',
+    'fib2module.c',  # note: this assumes f2py was manually run before!
+  ],
+  incdir_f2py / 'fortranobject.c',
+  include_directories: inc_np,
+  dependencies : py_dep,
+  install : true
+)
diff --git a/doc/source/f2py/code/meson_upd.build b/doc/source/f2py/code/meson_upd.build
index 44d69d182..5e4b13bae 100644
--- a/doc/source/f2py/code/meson_upd.build
+++ b/doc/source/f2py/code/meson_upd.build
@@ -1,37 +1,38 @@
 project('f2py_examples', 'c',
   version : '0.1',
-  default_options : ['warning_level=2'])
+  license: 'BSD-3',
+  meson_version: '>=0.64.0',
+  default_options : ['warning_level=2'],
+)
 
 add_languages('fortran')
 
 py_mod = import('python')
-py3 = py_mod.find_installation('python3')
-py3_dep = py3.dependency()
-message(py3.path())
-message(py3.get_install_dir())
+py = py_mod.find_installation(pure: false)
+py_dep = py.dependency()
 
-incdir_numpy = run_command(py3,
+incdir_numpy = run_command(py,
   ['-c', 'import os; os.chdir(".."); import numpy; print(numpy.get_include())'],
   check : true
 ).stdout().strip()
 
-incdir_f2py = run_command(py3,
+incdir_f2py = run_command(py,
     ['-c', 'import os; os.chdir(".."); import numpy.f2py; print(numpy.f2py.get_include())'],
     check : true
 ).stdout().strip()
 
 fibby_source = custom_target('fibbymodule.c',
-                            input : ['fib1.f'], # .f so no F90 wrappers
-                            output : ['fibbymodule.c', 'fibby-f2pywrappers.f'],
-                            command : [ py3, '-m', 'numpy.f2py', '@INPUT@',
-                            '-m', 'fibby', '--lower'])
+  input : ['fib1.f'],  # .f so no F90 wrappers
+  output : ['fibbymodule.c', 'fibby-f2pywrappers.f'],
+  command : [py, '-m', 'numpy.f2py', '@INPUT@', '-m', 'fibby', '--lower']
+)
 
 inc_np = include_directories(incdir_numpy, incdir_f2py)
 
-py3.extension_module('fibby',
-           'fib1.f',
-           fibby_source,
-           incdir_f2py+'/fortranobject.c',
-           include_directories: inc_np,
-           dependencies : py3_dep,
-           install : true)
+py.extension_module('fibby',
+  ['fib1.f', fibby_source],
+  incdir_f2py / 'fortranobject.c',
+  include_directories: inc_np,
+  dependencies : py_dep,
+  install : true
+)