numpy · mattip · May 18, 2023 · May 9, 2023 · May 18, 2023
diff --git a/building_with_meson.md b/building_with_meson.md
@@ -9,11 +9,11 @@ into a problem._
 
 **Install build tools:** Use one of:
 
-- `mamba env create -f environment.yml && mamba activate numpy-dev
+- `mamba env create -f environment.yml && mamba activate numpy-dev`
 
-- `python -m pip install -r build_requirements.txt
-  # also make sure you have pkg-config and the usual system dependencies for
-  # NumPy`
+- `python -m pip install -r build_requirements.txt`
+  *Note: also make sure you have `pkg-config` and the usual system dependencies
+  for NumPy*
 
 Then install spin:
 - `python -m pip install spin`
@@ -42,10 +42,10 @@ Note that `pip` will use the default build system, which is (as of now) still
 `build-backend = "mesonpy"` line at the top of `pyproject.toml`.
 
 After that is done, `pip install .` or `pip install --no-build-isolation .`
-will work as expected. As does building an sdist or wheel with `python -m build`.
-Note, however, that `pip install -e .` (in-place developer install) does not!
-Use `spin` instead (see above).
-
+will work as expected. As does building an sdist or wheel with `python -m build`,
+or `pip install -e . --no-build-isolation` for an editable install.
+For a more complete developer experience than editable installs, consider using
+`spin` instead though (see above).
 
 
 ### Workaround for a hiccup on Fedora

diff --git a/meson.build b/meson.build
@@ -6,7 +6,7 @@ project(
   # See `numpy/__init__.py`
   version: '1.24.0.dev0',
   license: 'BSD-3',
-  meson_version: '>= 0.64.0',
+  meson_version: '>= 1.1.0',
   default_options: [
     'buildtype=debugoptimized',
     'b_ndebug=if-release',
@@ -22,6 +22,7 @@ fs = import('fs')
 
 cc = meson.get_compiler('c')
 cpp = meson.get_compiler('cpp')
+cy = meson.get_compiler('cython')
 
 # Check compiler is recent enough (see the SciPy Toolchain Roadmap for details)
 if cc.get_id() == 'gcc'
@@ -34,16 +35,24 @@ elif cc.get_id() == 'msvc'
           'when building with MSVC')
   endif
 endif
+if not cy.version().version_compare('>=0.29.34')
+  error('NumPy requires Cython >= 0.29.34')
+endif
 
-# https://mesonbuild.com/Python-module.html
-py_mod = import('python')
-py = py_mod.find_installation(pure: false)
+py = import('python').find_installation(pure: false)
 py_dep = py.dependency()
 
 if not cc.has_header('Python.h', dependencies: py_dep)
   error('Cannot compile `Python.h`. Perhaps you need to install python-dev|python-devel')
 endif
 
+# Add default compile flags for any compiler that supports them.
+# Note that MSVC does not support strict aliasing at all, and neither do the
+# Intel compilers on Windows, so the `-fno` flavor of the flag should be fine.
+add_project_arguments(
+  cc.get_supported_arguments( '-fno-strict-aliasing'), language : 'c'
+)
+
 # Generate version number. Note that this will not (yet) update the version
 # number seen by pip or reflected in wheel filenames. See
 # https://github.com/mesonbuild/meson-python/issues/159 for that.

diff --git a/meson_options.txt b/meson_options.txt
@@ -2,12 +2,12 @@ option('blas', type: 'string', value: 'openblas',
         description: 'option for BLAS library switching')
 option('lapack', type: 'string', value: 'openblas',
         description: 'option for LAPACK library switching')
-option('disable-svml', type: 'boolean', value: 'false',
+option('disable-svml', type: 'boolean', value: false,
         description: 'Disable building against SVML')
-option('disable-threading', type: 'boolean', value: 'false',
+option('disable-threading', type: 'boolean', value: false,
         description: 'Disable threading support (see `NPY_ALLOW_THREADS` docs)')
 # TODO: flip value to 'false' once we have `npy_cpu_dispatch_config.h` & co.
-option('disable-simd-optimizations', type: 'boolean', value: 'true',
+option('disable-simd-optimizations', type: 'boolean', value: true,
         description: 'Disable SIMD features beyond the baseline ones')
-option('relaxed-strides-debug', type: 'boolean', value: 'false',
+option('relaxed-strides-debug', type: 'boolean', value: false,
         description: 'Enable relaxed strides debug mode (see `NPY_RELAXED_STRIDES_DEBUG` docs)')
diff --git a/numpy/core/src/umath/override.c b/numpy/core/src/umath/override.c
@@ -315,10 +315,9 @@ PyUFunc_CheckOverride(PyUFuncObject *ufunc, char *method,
 
     /* Call __array_ufunc__ functions in correct order */
     while (1) {
-        PyObject *override_obj;
-        PyObject *override_array_ufunc;
+        PyObject *override_obj = NULL;
+        PyObject *override_array_ufunc = NULL;
 
-        override_obj = NULL;
         *result = NULL;
 
         /* Choose an overriding argument */

diff --git a/numpy/meson.build b/numpy/meson.build
@@ -11,23 +11,15 @@ endif
 is_windows = host_machine.system() == 'windows'
 is_mingw = is_windows and cc.get_id() == 'gcc'
 
-if is_windows
+if is_mingw
   # For mingw-w64, link statically against the UCRT.
   gcc_link_args = ['-lucrt', '-static']
-  if is_mingw
-    add_project_link_arguments(gcc_link_args, language: ['c', 'cpp'])
-    # Force gcc to float64 long doubles for compatibility with MSVC
-    # builds, for C only.
-    add_project_arguments('-mlong-double-64', language: 'c')
-    # Make fprintf("%zd") work (see https://github.com/rgommers/scipy/issues/118)
-    add_project_arguments('-D__USE_MINGW_ANSI_STDIO=1', language: ['c', 'cpp'])
-    # Manual add of MS_WIN64 macro when not using MSVC.
-    # https://bugs.python.org/issue28267
-    bitness = run_command('_build_utils/gcc_build_bitness.py').stdout().strip()
-    if bitness == '64'
-      add_project_arguments('-DMS_WIN64', language: ['c', 'cpp'])
-    endif
-  endif
+  add_project_link_arguments(gcc_link_args, language: ['c', 'cpp'])
+  # Force gcc to float64 long doubles for compatibility with MSVC
+  # builds, for C only.
+  add_project_arguments('-mlong-double-64', language: 'c')
+  # Make fprintf("%zd") work (see https://github.com/rgommers/scipy/issues/118)
+  add_project_arguments('-D__USE_MINGW_ANSI_STDIO=1', language: ['c', 'cpp'])
 endif
 
 # Enable UNIX large file support on 32-bit systems (64 bit off_t,
@@ -58,13 +50,27 @@ lapack_name = get_option('lapack')
 # pkg-config uses a lower-case name while CMake uses a capitalized name, so try
 # that too to make the fallback detection with CMake work
 if blas_name == 'openblas'
-  blas_name = ['openblas', 'OpenBLAS']
+  blas = dependency(['openblas', 'OpenBLAS'], required: false)
+else
+  blas = dependency(blas_name, required: false)
+endif
+have_blas = blas.found()
+if have_blas and blas_name == 'blas'
+  # Netlib BLAS has a separate `libcblas.so` which we use directly in the g77
+  # ABI wrappers, so detect it and error out if we cannot find it.
+  # In the future, this should be done automatically for:
+  #   `dependency('blas', modules: cblas)`
+  # see https://github.com/mesonbuild/meson/pull/10921.
+  cblas = dependency('cblas')
+else
+  cblas = []
 endif
+
 if lapack_name == 'openblas'
   lapack_name = ['openblas', 'OpenBLAS']
 endif
-blas = dependency(blas_name, required: false)
 lapack = dependency(lapack_name, required: false)
+have_lapack = lapack.found()
 
 dependency_map = {
   'BLAS': blas,
@@ -74,8 +80,6 @@ dependency_map = {
 # BLAS and LAPACK are optional dependencies for NumPy. We can only use a BLAS
 # which provides a CBLAS interface.
 # TODO: add ILP64 support
-have_blas = blas.found() # TODO: and blas.has_cblas()
-have_lapack = lapack.found()
 if have_blas
   # TODO: this is a shortcut - it needs to be checked rather than used
   # unconditionally, and then added to the extension modules that need the

diff --git a/tools/ci/cirrus_macosx_arm64.yml b/tools/ci/cirrus_macosx_arm64.yml
@@ -37,9 +37,11 @@ macos_arm64_test_task:
     python --version
 
     RUNNER_OS="macOS"
-    CFLAGS="-std=c99 -fno-strict-aliasing"
     SDKROOT=/Applications/Xcode-14.0.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk
 
+    # NOTE: OpenBLAS is not used in this job; if that's done in the future, ensure
+    # PKG_CONFIG_PATH points to the directory containing the openblas.pc file
+    # that's installed with the cibw_before_build.sh command.
     # used for installing OpenBLAS/gfortran
     bash tools/wheels/cibw_before_build.sh $PWD