Issue #25136: Support Apple Xcode 7's new textual SDK stub libraries.

As of Xcode 7, SDKs for Apple platforms now include textual-format stub
libraries whose file names have a .tbd extension rather than the
standard OS X .dylib extension.  The Apple compiler tool chain handles
these stub libraries transparently and the installed system shared libraries
are still .dylibs.  However, the new stub libraries cause problems for
third-party programs that support building with Apple SDKs and make
build-time decisions based on the presence or paths of system-supplied
shared libraries in the SDK.  In particular, building Python itself with
an SDK fails to find system-supplied libraries during setup.py's build of
standard library extension modules.  The solution is to have
find_library_file() in Distutils search for .tbd files, along with
the existing types (.a, .so, and .dylib).  Patch by Tim Smith.

Lib/distutils/ccompiler.py

@@ -875,9 +875,9 @@ main (int argc, char **argv) {
     def library_filename(self, libname, lib_type='static',     # or 'shared'
                          strip_dir=0, output_dir=''):
         assert output_dir is not None
-        if lib_type not in ("static", "shared", "dylib"):
+        if lib_type not in ("static", "shared", "dylib", "xcode_stub"):
             raise ValueError(
-                  "'lib_type' must be \"static\", \"shared\" or \"dylib\"")
+                  "'lib_type' must be \"static\", \"shared\", \"dylib\", or \"xcode_stub\"")
         fmt = getattr(self, lib_type + "_lib_format")
         ext = getattr(self, lib_type + "_lib_extension")
 

Lib/distutils/unixccompiler.py

@@ -76,7 +76,9 @@ class UnixCCompiler(CCompiler):
     static_lib_extension = ".a"
     shared_lib_extension = ".so"
     dylib_lib_extension = ".dylib"
+    xcode_stub_lib_extension = ".tbd"
     static_lib_format = shared_lib_format = dylib_lib_format = "lib%s%s"
+    xcode_stub_lib_format = dylib_lib_format
     if sys.platform == "cygwin":
         exe_extension = ".exe"
 
@@ -255,12 +257,28 @@ class UnixCCompiler(CCompiler):
     def find_library_file(self, dirs, lib, debug=0):
         shared_f = self.library_filename(lib, lib_type='shared')
         dylib_f = self.library_filename(lib, lib_type='dylib')
+        xcode_stub_f = self.library_filename(lib, lib_type='xcode_stub')
         static_f = self.library_filename(lib, lib_type='static')
 
         if sys.platform == 'darwin':
             # On OSX users can specify an alternate SDK using
             # '-isysroot', calculate the SDK root if it is specified
             # (and use it further on)
+            #
+            # Note that, as of Xcode 7, Apple SDKs may contain textual stub
+            # libraries with .tbd extensions rather than the normal .dylib
+            # shared libraries installed in /.  The Apple compiler tool
+            # chain handles this transparently but it can cause problems
+            # for programs that are being built with an SDK and searching
+            # for specific libraries.  Callers of find_library_file need to
+            # keep in mind that the base filename of the returned SDK library
+            # file might have a different extension from that of the library
+            # file installed on the running system, for example:
+            #   /Applications/Xcode.app/Contents/Developer/Platforms/
+            #       MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/
+            #       usr/lib/libedit.tbd
+            # vs
+            #   /usr/lib/libedit.dylib
             cflags = sysconfig.get_config_var('CFLAGS')
             m = re.search(r'-isysroot\s+(\S+)', cflags)
             if m is None:
@@ -274,6 +292,7 @@ class UnixCCompiler(CCompiler):
             shared = os.path.join(dir, shared_f)
             dylib = os.path.join(dir, dylib_f)
             static = os.path.join(dir, static_f)
+            xcode_stub = os.path.join(dir, xcode_stub_f)
 
             if sys.platform == 'darwin' and (
                 dir.startswith('/System/') or (
@@ -282,6 +301,7 @@ class UnixCCompiler(CCompiler):
                 shared = os.path.join(sysroot, dir[1:], shared_f)
                 dylib = os.path.join(sysroot, dir[1:], dylib_f)
                 static = os.path.join(sysroot, dir[1:], static_f)
+                xcode_stub = os.path.join(sysroot, dir[1:], xcode_stub_f)
 
             # We're second-guessing the linker here, with not much hard
             # data to go on: GCC seems to prefer the shared library, so I'm
@@ -289,6 +309,8 @@ class UnixCCompiler(CCompiler):
             # ignoring even GCC's "-static" option.  So sue me.
             if os.path.exists(dylib):
                 return dylib
+            elif os.path.exists(xcode_stub):
+                return xcode_stub
             elif os.path.exists(shared):
                 return shared
             elif os.path.exists(static):

Misc/NEWS

@@ -270,6 +270,8 @@ Build
 - Issue #26268: Update OS X 10.5 installer and Windows builds to use
   OpenSSL 1.0.2f.
 
+- Issue #25136: Support Apple Xcode 7's new textual SDK stub libraries.
+
 Windows
 -------
 

setup.py

@@ -136,6 +136,22 @@ def find_library_file(compiler, libname, std_dirs, paths):
         p = p.rstrip(os.sep)
 
         if host_platform == 'darwin' and is_macosx_sdk_path(p):
+            # Note that, as of Xcode 7, Apple SDKs may contain textual stub
+            # libraries with .tbd extensions rather than the normal .dylib
+            # shared libraries installed in /.  The Apple compiler tool
+            # chain handles this transparently but it can cause problems
+            # for programs that are being built with an SDK and searching
+            # for specific libraries.  Distutils find_library_file() now
+            # knows to also search for and return .tbd files.  But callers
+            # of find_library_file need to keep in mind that the base filename
+            # of the returned SDK library file might have a different extension
+            # from that of the library file installed on the running system,
+            # for example:
+            #   /Applications/Xcode.app/Contents/Developer/Platforms/
+            #       MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/
+            #       usr/lib/libedit.tbd
+            # vs
+            #   /usr/lib/libedit.dylib
             if os.path.join(sysroot, p[1:]) == dirname:
                 return [ ]