MSVC complex values (GraphBLAS#68)

* MSVC complex values

* Give build.py a more unique name

MANIFEST.in

@@ -1,4 +1,5 @@
 include setup.py
+include build_graphblas_cffi.py
 include README.md
 include LICENSE
 include suitesparse_graphblas/*.pxd

build_graphblas_cffi.py

@@ -0,0 +1,70 @@
+import os
+import sys
+from pathlib import Path
+
+from cffi import FFI
+from setuptools import Extension
+
+is_win = sys.platform.startswith("win")
+ss_g = Path(__file__).parent / "suitesparse_graphblas"
+
+ffibuilder = FFI()
+
+include_dirs = [os.path.join(sys.prefix, "include")]
+library_dirs = [os.path.join(sys.prefix, "lib")]
+if is_win:
+    include_dirs.append(os.path.join(sys.prefix, "Library", "include"))
+    library_dirs.append(os.path.join(sys.prefix, "Library", "lib"))
+
+ffibuilder.set_source(
+    "suitesparse_graphblas._graphblas",
+    (ss_g / "source.c").read_text(),
+    libraries=["graphblas"],
+    include_dirs=include_dirs,
+    library_dirs=library_dirs,
+)
+
+ffibuilder.cdef((ss_g / "suitesparse_graphblas.h").read_text())
+
+
+def get_extension(apply_msvc_patch: bool = None, extra_compile_args=()):
+    """
+    Get a setuptools.Extension version of this CFFI builder.
+
+    In other words, enables `setup(ext_modules=[get_extension()])`
+    instead of `setup(cffi_modules=["build_graphblas_cffi.py:ffibuilder"])`.
+
+    The main reason for this is to allow a patch for complex values when compiling on MSVC.
+    MSVC famously lacks support for standard C complex types like `double _Complex` and
+    `float _Complex`. Instead, MSVC has its own `_Dcomplex` and `_Fcomplex` types.
+    Cffi's machinery cannot be made to work with these types, so we instead
+    emit the regular standard C code and patch it manually.
+
+    :param apply_msvc_patch: whether to apply the MSVC patch.
+    If None then auto-detect based on platform.
+    :param extra_compile_args: forwarded to Extension constructor.
+    """
+    code_path = ss_g / "_graphblas.c"
+    ffibuilder.emit_c_code(str(code_path))
+
+    if apply_msvc_patch is None:
+        apply_msvc_patch = is_win
+
+    if apply_msvc_patch:
+        msvc_code = code_path.read_text()
+        msvc_code = msvc_code.replace("float _Complex", "_Fcomplex")
+        msvc_code = msvc_code.replace("double _Complex", "_Dcomplex")
+        code_path.write_text(msvc_code)
+
+    return Extension(
+        "suitesparse_graphblas._graphblas",
+        [os.path.join("suitesparse_graphblas", "_graphblas.c")],
+        libraries=["graphblas"],
+        include_dirs=include_dirs,
+        library_dirs=library_dirs,
+        extra_compile_args=extra_compile_args,
+    )
+
+
+if __name__ == "__main__":
+    ffibuilder.compile(verbose=True)

setup.py

@@ -5,6 +5,10 @@
 import numpy as np
 from setuptools import Extension, setup
 
+# Add current directory to the Python path because it's not present when running `pip install .`
+sys.path.append(os.path.dirname(__file__))
+import build_graphblas_cffi  # noqa: E402 # isort:skip
+
 try:
     from Cython.Build import cythonize
     from Cython.Compiler.Options import get_directive_defaults
@@ -15,6 +19,13 @@
 
 define_macros = [("NPY_NO_DEPRECATED_API", "NPY_1_7_API_VERSION")]
 
+# /d2FH4- flag needed only for early Python 3.8 builds on Windows.
+# See https://cibuildwheel.readthedocs.io/en/stable/faq/
+# (Search for flag on page. Full link is long and causes the linter to fail the tests.)
+#
+# The /std:c11 flag is because the MSVC default is C89.
+extra_compile_args = ["/d2FH4-", "/std:c11"] if sys.platform == "win32" else []
+
 if use_cython:
     suffix = ".pyx"
     directive_defaults = get_directive_defaults()
@@ -40,13 +51,15 @@
         [name],
         include_dirs=include_dirs,
         define_macros=define_macros,
+        extra_compile_args=extra_compile_args,
     )
     for name in glob(f"suitesparse_graphblas/**/*{suffix}", recursive=True)
 ]
 if use_cython:
     ext_modules = cythonize(ext_modules, include_path=include_dirs)
 
+ext_modules.append(build_graphblas_cffi.get_extension(extra_compile_args=extra_compile_args))
+
 setup(
     ext_modules=ext_modules,
-    cffi_modules=["suitesparse_graphblas/build.py:ffibuilder"],
 )