[PATCH] bindings: python: fix out-of-source build

[jf@xxxxxxxxxxxxxxxxxxx]

From: Joerg Faschingbauer <jf@xxxxxxxxxxxxxxxxxxx>

Makefile.am delegates the build of the python extension to its
setup.py file, which references the extension .c files relative to the
source dir. This makes it impossible to build in a directory that is
different from the source directory (for example, for PC and ARM but
from the same source).

* Modify Makefile.am to pass automake's $(srcdir) into setup.py via
  GPIOD_SRCDIR environment variable.
* Modify setup.py to pick up .c files relative from that directory.
---
 bindings/python/Makefile.am |  6 ++++--
 bindings/python/setup.py    | 23 ++++++++++++++---------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/bindings/python/Makefile.am b/bindings/python/Makefile.am
index 3212a8f..6c2f99b 100644
--- a/bindings/python/Makefile.am
+++ b/bindings/python/Makefile.am
@@ -12,13 +12,15 @@ endif
 all-local:
 	GPIOD_VERSION_STRING=$(VERSION_STR) \
 	GPIOD_WITH_TESTS=$(BUILD_TESTS) \
-	$(PYTHON) setup.py build_ext --inplace \
+	GPIOD_SRCDIR=$(srcdir) \
+	$(PYTHON) $(srcdir)/setup.py build_ext --inplace \
 		--include-dirs=$(top_srcdir)/include/:$(top_srcdir)/tests/gpiosim/ \
 		--library-dirs=$(top_builddir)/lib/.libs/:$(top_srcdir)/tests/gpiosim/.libs/
 
 install-exec-local:
 	GPIOD_WITH_TESTS= \
-	$(PYTHON) setup.py install --prefix=$(prefix)
+	GPIOD_SRCDIR=$(srcdir) \
+	$(PYTHON) $(srcdir)/setup.py install --prefix=$(prefix)
 
 SUBDIRS = gpiod
 
diff --git a/bindings/python/setup.py b/bindings/python/setup.py
index a951069..3ab01e1 100644
--- a/bindings/python/setup.py
+++ b/bindings/python/setup.py
@@ -2,17 +2,22 @@
 # SPDX-FileCopyrightText: 2022 Bartosz Golaszewski <brgl@xxxxxxxx>
 
 from os import environ
+import os.path
 from setuptools import setup, Extension, find_packages
 
+srcdir = environ.get('GPIOD_SRCDIR', '.')
+def src(path):
+    return os.path.join(srcdir, path)
+
 gpiod_ext = Extension(
     "gpiod._ext",
     sources=[
-        "gpiod/ext/chip.c",
-        "gpiod/ext/common.c",
-        "gpiod/ext/line-config.c",
-        "gpiod/ext/line-settings.c",
-        "gpiod/ext/module.c",
-        "gpiod/ext/request.c",
+        src("gpiod/ext/chip.c"),
+        src("gpiod/ext/common.c"),
+        src("gpiod/ext/line-config.c"),
+        src("gpiod/ext/line-settings.c"),
+        src("gpiod/ext/module.c"),
+        src("gpiod/ext/request.c"),
     ],
     define_macros=[("_GNU_SOURCE", "1")],
     libraries=["gpiod"],
@@ -21,7 +26,7 @@ gpiod_ext = Extension(
 
 gpiosim_ext = Extension(
     "tests.gpiosim._ext",
-    sources=["tests/gpiosim/ext.c"],
+    sources=[src("tests/gpiosim/ext.c")],
     define_macros=[("_GNU_SOURCE", "1")],
     libraries=["gpiosim"],
     extra_compile_args=["-Wall", "-Wextra"],
@@ -29,7 +34,7 @@ gpiosim_ext = Extension(
 
 procname_ext = Extension(
     "tests.procname._ext",
-    sources=["tests/procname/ext.c"],
+    sources=[src("tests/procname/ext.c")],
     define_macros=[("_GNU_SOURCE", "1")],
     extra_compile_args=["-Wall", "-Wextra"],
 )
@@ -39,7 +44,7 @@ if "GPIOD_WITH_TESTS" in environ and environ["GPIOD_WITH_TESTS"] == "1":
     extensions.append(gpiosim_ext)
     extensions.append(procname_ext)
 
-with open("gpiod/version.py", "r") as fd:
+with open(src("gpiod/version.py"), "r") as fd:
     exec(fd.read())
 
 setup(
-- 
2.38.1