always precompile xcffib’s ffi (even in ABI mode)

.gitignore

@@ -4,6 +4,7 @@ dist-newstyle
 _*.c
 _*.so
 _*.o
+_xcffib.py
 *.swp
 *.swo
 *.pyc

module/__init__.py

@@ -25,17 +25,23 @@
 
 
 # Attempt api mode if installed
-api_mode = True
+cffi_mode = "(unknown)"
 try:
+    # Note in ABI mode lib will be missing
     from _xcffib import ffi, lib
-    api_mode = True
+    assert lib.__CFFI_MODE == lib.__CFFI_MODE_API
+    cffi_mode = "API"
 except ImportError:
-    api_mode = False
-
-# Fall back to non api mode
-if not api_mode:
-    from .ffi_build import ffi  # noqa
-
+    try:
+        # Note in ABI mode lib will be missing
+        from _xcffib import ffi
+    except ImportError:
+        # Fall back to importing and parsing cffi defs
+        from .ffi_build import ffi
+
+# Fall back to non api mode, inline at load time
+# this would only happen if the precompiled _xcffib was missing
+if cffi_mode != "API":
     if platform.system() == "Darwin":
         soname = "libxcb.dylib"
     elif platform.system() == "Windows":
@@ -45,6 +51,10 @@
         if soname is None:
             soname = "libxcb.so"
     lib = ffi.dlopen(soname)  # noqa
+    if lib.__CFFI_MODE == lib.__CFFI_MODE_ABI:
+        cffi_mode = "ABI"
+    elif lib.__CFFI_MODE == lib.__CFFI_MODE_ABI_PRECOMPILED:
+        cffi_mode = "ABI(precompiled)"
 
 __xcb_proto_version__ = 'placeholder'
 __version__ = 'placeholder'

module/ffi_build.py

@@ -13,7 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import os
+import sys
+from warnings import warn
 
 from cffi import FFI
 
@@ -237,29 +238,76 @@
     xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie);
 """
 
-CDEF += """
+CDEF += r"""
     unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *request);
     void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e);
     int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error);
     void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence);
 """
 
+__CFFI_MODE_API = 0
+__CFFI_MODE_ABI = 1
+__CFFI_MODE_ABI_PRECOMPILED = 2
+CDEF += f"""
+#define __CFFI_MODE_API {__CFFI_MODE_API}
+#define __CFFI_MODE_ABI {__CFFI_MODE_ABI}
+#define __CFFI_MODE_ABI_PRECOMPILED {__CFFI_MODE_ABI_PRECOMPILED}
+"""
+
+
+def ffi_build(build_source=True):
+    """
+    This will be called from setup() to return an FFI
+    which it will compile - work out here which type is
+    possible and return it.
+    """
+    # Note local ffi needed here as multiple
+    # source calls is illegal and cdefs differ
+    try:
+        ffi = FFI()
+        ffi.cdef(CDEF + f"""
+            #define __CFFI_MODE {__CFFI_MODE_API}
+        """)
+
+        ffi.set_source_pkgconfig(
+            '_xcffib',
+            ['xcb'],
+            """
+            #include "xcb/xcb.h"
+            #include "xcb/xproto.h"
+            #include "xcb/xcbext.h"
+            #include "xcb/render.h"
+            """ + f"""
+                #define __CFFI_MODE_API {__CFFI_MODE_API}
+                #define __CFFI_MODE_ABI {__CFFI_MODE_ABI}
+                #define __CFFI_MODE_ABI_PRECOMPILED {__CFFI_MODE_ABI_PRECOMPILED}
+                #define __CFFI_MODE {__CFFI_MODE_API}
+            """
+        )
+
+        ffi.compile(verbose=True)
+        return ffi
+    except Exception:
+        warn("Falling back to precompiled python mode")
+        ffi = FFI()
+        ffi.cdef(CDEF + f"""
+            #define __CFFI_MODE {__CFFI_MODE_ABI_PRECOMPILED}
+        """)
+
+        ffi.set_source(
+            '_xcffib',
+            None)
 
-ffi = FFI()
-ffi.cdef(CDEF)
-
-if ('XCFFIB_API_MODE' in os.environ and
-        int(os.environ['XCFFIB_API_MODE']) == 1):
-    ffi.set_source_pkgconfig(
-        '_xcffib',
-        ['xcb'],
-        """
-        #include "xcb/xcb.h"
-        #include "xcb/xproto.h"
-        #include "xcb/xcbext.h"
-        #include "xcb/render.h"
-        """
-    )
-
-    if __name__ == "__main__":
         ffi.compile(verbose=True)
+        return ffi
+
+
+ffi = FFI()
+ffi.cdef(CDEF + f"""
+    #define __CFFI_MODE {__CFFI_MODE_ABI}
+""")
+
+
+if __name__ == "__main__":
+    ffi = ffi_build()
+    ffi.compile(verbose=True)

setup.py

@@ -47,11 +47,6 @@ def finalize_options(self):
 version = "1.5.0"
 dependencies = ["cffi>=1.1.0; python_implementation != 'PyPy'"]
 
-api_mode = False
-if ('XCFFIB_API_MODE' in os.environ and
-        int(os.environ['XCFFIB_API_MODE']) == 1):
-    api_mode = True
-
 setup(
     name="xcffib",
     version=version,
@@ -78,5 +73,5 @@ def finalize_options(self):
         'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Software Development :: Libraries'
     ],
-    cffi_modules=["xcffib/ffi_build.py:ffi"] if api_mode else [],
+    cffi_modules=["xcffib/ffi_build.py:ffi_build"]
 )