bpo-45800: Move pyexpat build setup into configure (GH-29547)

Settings for :mod:`pyexpat` C extension are now detected by ``configure``.
The bundled ``expat`` library is built in ``Makefile``.

Signed-off-by: Christian Heimes <christian@python.org>

1 files changed, 87 insertions, 53 deletions

diff --git a/setup.py b/setup.py
index 86ce5d2..c62f042 100644
--- a/setup.py
+++ b/setup.py
@@ -364,6 +364,57 @@ def find_module_file(module, dirlist):
     return os.path.join(dirs[0], module)
 
 
+def parse_cflags(flags):
+    """Parse a string with compiler flags (-I, -D, -U, extra)
+    
+    Distutils appends extra args to the compiler arguments. Some flags like
+    -I must appear earlier. Otherwise the pre-processor picks up files
+    from system inclue directories.
+    """
+    include_dirs = []
+    define_macros = []
+    undef_macros = []
+    extra_compile_args = []
+    if flags is not None:
+        # shlex.split(None) reads from stdin
+        for token in shlex.split(flags):
+            switch = token[0:2]
+            value = token[2:]
+            if switch == '-I':
+                include_dirs.append(value)
+            elif switch == '-D':
+                key, _, val = value.partition("=")
+                if not val:
+                    val = None
+                define_macros.append((key, val))
+            elif switch == '-U':
+                undef_macros.append(value)
+            else:
+                extra_compile_args.append(token)
+
+    return include_dirs, define_macros, undef_macros, extra_compile_args
+
+
+def parse_ldflags(flags):
+    """Parse a string with linker flags (-L, -l, extra)"""
+    library_dirs = []
+    libraries = []
+    extra_link_args = []
+    if flags is not None:
+        # shlex.split(None) reads from stdin
+        for token in shlex.split(flags):
+            switch = token[0:2]
+            value = token[2:]
+            if switch == '-L':
+                library_dirs.append(value)
+            elif switch == '-l':
+                libraries.append(value)
+            else:
+                extra_link_args.append(token)
+
+    return library_dirs, libraries, extra_link_args
+
+
 class PyBuildExt(build_ext):
 
     def __init__(self, dist):
@@ -1469,59 +1520,39 @@ class PyBuildExt(build_ext):
         #
         # More information on Expat can be found at www.libexpat.org.
         #
-        if '--with-system-expat' in sysconfig.get_config_var("CONFIG_ARGS"):
-            expat_inc = []
-            extra_compile_args = []
-            expat_lib = ['expat']
-            expat_sources = []
-            expat_depends = []
-        else:
-            expat_inc = [os.path.join(self.srcdir, 'Modules', 'expat')]
-            extra_compile_args = []
-            # bpo-44394: libexpat uses isnan() of math.h and needs linkage
-            # against the libm
-            expat_lib = ['m']
-            expat_sources = ['expat/xmlparse.c',
-                             'expat/xmlrole.c',
-                             'expat/xmltok.c']
-            expat_depends = ['expat/ascii.h',
-                             'expat/asciitab.h',
-                             'expat/expat.h',
-                             'expat/expat_config.h',
-                             'expat/expat_external.h',
-                             'expat/internal.h',
-                             'expat/latin1tab.h',
-                             'expat/utf8tab.h',
-                             'expat/xmlrole.h',
-                             'expat/xmltok.h',
-                             'expat/xmltok_impl.h'
-                             ]
-
-            cc = sysconfig.get_config_var('CC').split()[0]
-            ret = run_command(
-                      '"%s" -Werror -Wno-unreachable-code -E -xc /dev/null >/dev/null 2>&1' % cc)
-            if ret == 0:
-                extra_compile_args.append('-Wno-unreachable-code')
+        cflags = parse_cflags(sysconfig.get_config_var("EXPAT_CFLAGS"))
+        include_dirs, define_macros, undef_macros, extra_compile_args = cflags
+        # ldflags includes either system libexpat or full path to
+        # our static libexpat.a.
+        ldflags = parse_ldflags(sysconfig.get_config_var("EXPAT_LDFLAGS"))
+        library_dirs, libraries, extra_link_args = ldflags
+
+        expat_depends = []
+        libexpat_a = sysconfig.get_config_var("LIBEXPAT_A")
+        if libexpat_a:
+            expat_depends.append(libexpat_a)
 
         self.add(Extension('pyexpat',
+                           include_dirs=include_dirs,
+                           define_macros=define_macros,
+                           undef_macros=undef_macros,
                            extra_compile_args=extra_compile_args,
-                           include_dirs=expat_inc,
-                           libraries=expat_lib,
-                           sources=['pyexpat.c'] + expat_sources,
+                           library_dirs=library_dirs,
+                           libraries=libraries,
+                           extra_link_args=extra_link_args,
+                           sources=['pyexpat.c'],
                            depends=expat_depends))
 
         # Fredrik Lundh's cElementTree module.  Note that this also
         # uses expat (via the CAPI hook in pyexpat).
-
-        if os.path.isfile(os.path.join(self.srcdir, 'Modules', '_elementtree.c')):
-            self.add(Extension('_elementtree',
-                               include_dirs=expat_inc,
-                               libraries=expat_lib,
-                               sources=['_elementtree.c'],
-                               depends=['pyexpat.c', *expat_sources,
-                                        *expat_depends]))
-        else:
-            self.missing.append('_elementtree')
+        self.add(Extension('_elementtree',
+                           include_dirs=include_dirs,
+                           define_macros=define_macros,
+                           undef_macros=undef_macros,
+                           extra_compile_args=extra_compile_args,
+                           # no EXPAT_LDFLAGS
+                           sources=['_elementtree.c'],
+                           depends=['pyexpat.c', *expat_depends]))
 
     def detect_multibytecodecs(self):
         # Hye-Shik Chang's CJKCodecs modules.
@@ -2019,15 +2050,14 @@ class PyBuildExt(build_ext):
         # Stefan Krah's _decimal module
         sources = ['_decimal/_decimal.c']
         depends = ['_decimal/docstrings.h']
-        define_macros = []
-                
-        cflags = sysconfig.get_config_var("DECIMAL_CFLAGS")
-        extra_compile_args = shlex.split(cflags) if cflags else None
+
+        cflags = parse_cflags(sysconfig.get_config_var("DECIMAL_CFLAGS"))
+        include_dirs, define_macros, undef_macros, extra_compile_args = cflags
         # ldflags includes either system libmpdec or full path to
         # our static libmpdec.a.
-        ldflags = sysconfig.get_config_var("DECIMAL_LDFLAGS")
-        extra_link_args = shlex.split(ldflags) if ldflags else None
-        
+        ldflags = parse_ldflags(sysconfig.get_config_var("DECIMAL_LDFLAGS"))
+        library_dirs, libraries, extra_link_args = ldflags
+
         libmpdec_a = sysconfig.get_config_var("LIBMPDEC_A")
         if libmpdec_a:
             depends.append(libmpdec_a)
@@ -2035,8 +2065,12 @@ class PyBuildExt(build_ext):
         # Uncomment for extra functionality:
         #define_macros.append(('EXTRA_FUNCTIONALITY', 1))
         self.add(Extension('_decimal',
+                           include_dirs=include_dirs,
                            define_macros=define_macros,
+                           undef_macros=undef_macros,
                            extra_compile_args=extra_compile_args,
+                           library_dirs=library_dirs,
+                           libraries=libraries,
                            extra_link_args=extra_link_args,
                            sources=sources,
                            depends=depends))