ENH: adjust default build options

Switch from debug=false, optimization=2 to buildtype=release. Despite
what the Meson documentation says, the former does not change the
default buildtype=debug, which undesired effects on other settings
derived from the value of the buildtype option.

Whit the default b_vscrt=from_buildtype option, Meson instructs the
MSVC compiler to use the debug version of the VS runtime library when
buildtype=debug. This causes the linker look for the debug build of
all the linked DLLs. The Python distribution for Windows does not
contain a debug version of the python.dll and linking fails. To avoid
this issue when the user explicitly asks for a debug build, also set
b_vscrt=mt.

The b_ndebug=if-release option set by meson-python also looks at the
value of the buildtype and not to the value of the debug options.
Setting buildtype=release has the desired effect of disabling
assertions.

The prefix, python.purelibdir, and python.platlibdir build options are
no more necessary after the heuristic for determining the location
where installed files need to be placer from their installation
location has been removed in #280. Remove them.

Fixes #381.

meson.build

@@ -17,7 +17,6 @@ py.install_sources(
   'mesonpy/_dylib.py',
   'mesonpy/_editable.py',
   'mesonpy/_elf.py',
-  'mesonpy/_introspection.py',
   'mesonpy/_tags.py',
   'mesonpy/_util.py',
   'mesonpy/_wheelfile.py',

mesonpy/__init__.py

@@ -48,7 +48,6 @@
 import mesonpy._compat
 import mesonpy._dylib
 import mesonpy._elf
-import mesonpy._introspection
 import mesonpy._tags
 import mesonpy._util
 import mesonpy._wheelfile
@@ -728,26 +727,15 @@ def _run(self, cmd: Sequence[str]) -> None:
 
     def _configure(self, reconfigure: bool = False) -> None:
         """Configure Meson project."""
-        sys_paths = mesonpy._introspection.SYSCONFIG_PATHS
         setup_args = [
-            f'--prefix={sys.base_prefix}',
             os.fspath(self._source_dir),
             os.fspath(self._build_dir),
             f'--native-file={os.fspath(self._meson_native_file)}',
-            # TODO: Allow configuring these arguments
-            '-Ddebug=false',
+            # default build options
+            '-Dbuildtype=release',
             '-Db_ndebug=if-release',
-            '-Doptimization=2',
-
-            # XXX: This should not be needed, but Meson is using the wrong paths
-            #      in some scenarios, like on macOS.
-            #      https://github.com/mesonbuild/meson-python/pull/87#discussion_r1047041306
-            '--python.purelibdir',
-            sys_paths['purelib'],
-            '--python.platlibdir',
-            sys_paths['platlib'],
-
-            # user args
+            '-Db_vscrt=md',
+            # user build options
             *self._meson_args['setup'],
         ]
         if reconfigure: