bt2: run swig by hand instead of through "setup.py build_ext"

When we build the bt2 Python module, we call "setup.py build_ext", which
runs swig to generate the .c file from .i files and builds the native
library.  We then run "setup.py build" to copy the Python files over to
build_lib directory.

However, "setup.py build" insists on running "build_ext" itself, seeing
that we have an ext_modules entry in our setup.py.  This results in the
.i -> .so process being run twice.  It's a bit wasteful to do the
process twice, but in itself it's not a big problem.

A bigger problem is that the second time swig is ran (through "setup.py
build"), it is done without honoring the SWIG Makefile variable. Here, I
have configured my build to use SWIG=/tmp/swig/bin/swig, and the two
swig invocations are:

    /tmp/swig/bin/swig -python -I/home/simark/src/babeltrace/include -o bt2/native_bt_wrap.c bt2/native_bt.i
    swig -python -I/home/simark/src/babeltrace/include -o bt2/native_bt_wrap.c bt2/native_bt.i

This means that trying to use a custom swig executable through the SWIG
configuration variable will not work, as it will always be overwritten
by the output of the "swig" in the path.

I haven't found a way to get the right swig executable to be used the
second time:

- "setup.py build" doesn't have a --swig option
- We can't use swig= in setup.py
- We can't override using an environment variable

The solution I found was to run swig ourselves to generate the .c file,
and feed that to the native extension built with distutils.  We now
don't need to call build_ext explicitly, since the call done through
"build" is sufficient.  It therefore fixes both problems: swigging and
building the library is now done only once, and the right swig
executable is used.

Change-Id: I9ed9d22fae1f5675d42af08e77607515dfdf788a
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1711
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>

diff --git a/src/bindings/python/bt2/Makefile.am b/src/bindings/python/bt2/Makefile.am
index 123ee2cfe20f38fb91e8e297ba80038e5ed39b5e..a3f0d88f18e9097e585107ac78b1263bf44c7ddf 100644 (file)
--- a/src/bindings/python/bt2/Makefile.am
+++ b/src/bindings/python/bt2/Makefile.am
@@ -5,9 +5,8 @@ AM_LDFLAGS=-L$(top_builddir)/src/lib/.libs
 
 INSTALLED_FILES=$(builddir)/installed_files.txt
 
-STATIC_BINDINGS_DEPS =                                 \
-       bt2/logging.c                                   \
-       bt2/logging.h                                   \
+SWIG_INTERFACE_FILES =                                 \
+       bt2/native_bt.i                                 \
        bt2/native_bt_clock_class.i                     \
        bt2/native_bt_clock_snapshot.i                  \
        bt2/native_bt_component_class.i                 \
@@ -19,7 +18,6 @@ STATIC_BINDINGS_DEPS =                                        \
        bt2/native_bt_field_path.i                      \
        bt2/native_bt_field.i                           \
        bt2/native_bt_graph.i                           \
-       bt2/native_bt.i                                 \
        bt2/native_bt_logging.i                         \
        bt2/native_bt_message.i                         \
        bt2/native_bt_message_iterator.i                \
@@ -32,7 +30,12 @@ STATIC_BINDINGS_DEPS =                                       \
        bt2/native_bt_trace_class.i                     \
        bt2/native_bt_trace.i                           \
        bt2/native_bt_value.i                           \
-       bt2/native_bt_version.i                         \
+       bt2/native_bt_version.i
+
+STATIC_BINDINGS_DEPS =                                 \
+       $(SWIG_INTERFACE_FILES)                         \
+       bt2/logging.c                                   \
+       bt2/logging.h                                   \
        bt2/clock_class.py                              \
        bt2/clock_snapshot.py                           \
        bt2/component.py                                \
@@ -62,6 +65,7 @@ STATIC_BINDINGS_DEPS =                                        \
 
 GENERATED_BINDINGS_DEPS =      \
        bt2/__init__.py         \
+       bt2/native_bt.c         \
        setup.py
 
 BUILD_FLAGS=CC="$(CC)" \
@@ -80,10 +84,16 @@ copy-static-deps.stamp: $(addprefix $(srcdir)/, $(STATIC_BINDINGS_DEPS))
        touch $@
 
 build-python-bindings.stamp: copy-static-deps.stamp $(GENERATED_BINDINGS_DEPS)
-       $(BUILD_FLAGS) $(PYTHON) $(builddir)/setup.py build_ext --force --swig "$(SWIG)"
        $(BUILD_FLAGS) $(PYTHON) $(builddir)/setup.py build --force
        touch $@
 
+swig_verbose = $(swig_verbose_@AM_V@)
+swig_verbose_ = $(swig_verbose_@AM_DEFAULT_V@)
+swig_verbose_0 = @echo "  SWIG     " $@;
+
+$(builddir)/bt2/native_bt.c: $(SWIG_INTERFACE_FILES)
+       $(swig_verbose)$(SWIG) -python -I"$(top_srcdir)/include" -o "$@" "$<"
+
 install-exec-local: build-python-bindings.stamp
        @opts="--prefix=$(prefix) --record $(INSTALLED_FILES) --verbose --no-compile $(DISTSETUPOPTS)"; \
        if [ "$(DESTDIR)" != "" ]; then \
@@ -114,4 +124,4 @@ uninstall-local:
 EXTRA_DIST = $(STATIC_BINDINGS_DEPS)
 
 # clean: generated C and Python files (by SWIG)
-CLEANFILES = bt2/native_bt.py bt2/native_bt_wrap.c build-python-bindings.stamp copy-static-deps.stamp
+CLEANFILES = bt2/native_bt.py bt2/native_bt.c build-python-bindings.stamp copy-static-deps.stamp

diff --git a/src/bindings/python/bt2/setup.py.in b/src/bindings/python/bt2/setup.py.in
index e57ac024dd6e399c4be1f4f902c3df9b0579f59b..682cbbc0c52ac7630af93624be84bfd9d387e16b 100644 (file)
--- a/src/bindings/python/bt2/setup.py.in
+++ b/src/bindings/python/bt2/setup.py.in
@@ -36,12 +36,11 @@ following command to your .bashrc/.zshrc:
 
 def main():
     babeltrace_ext = Extension('bt2._native_bt',
-                        sources=['bt2/native_bt.i', 'bt2/logging.c'],
+                        sources=['bt2/native_bt.c', 'bt2/logging.c'],
                         libraries=['babeltrace2', 'glib-2.0'],
                         extra_objects=['@top_builddir@/src/logging/.libs/libbabeltrace2-logging.a',
                             '@top_builddir@/src/common/.libs/libbabeltrace2-common.a',
-                            '@top_builddir@/src/py-common/.libs/libbabeltrace2-py-common.a'],
-                        swig_opts=['-I@top_srcdir@/include'])
+                            '@top_builddir@/src/py-common/.libs/libbabeltrace2-py-common.a'])
 
     dist = setup(name='bt2',
             version='@PACKAGE_VERSION@',