allow building GDB with Python support on MinGW

This makes several adjustements to the configure python-config.py
scripts to deal with the differences between a Unix install of Python
and a Windows install of Python (as downloaded from the Python website).

Differences:

  - The Python executable is directly in the python prefix directory
    as opposed to inside the bin/ subdirectory.

  - The name of the python library is does not have a dot in the version
    number: On Unix, we have libpython2.7, while on Windows, it's
    libpython27.  So the regexp extracting the python version from
    the Python lib filename had to be adjusted slightly.

    Also, the tests checking the name of the libpython had to be
    adjusted to allow for that.

  - There are no link options following the -lpython<version> switch
    on Windows, but the regexp extracting the python version was
    using it as a delimiter.  It had to be removed.

  - python-config.py does not work on Windows, mostly because
    some sysconfig variables are missing.  They are not necessary
    so the script was adapted to skip them if not defined.

  - The paths returned by python-config.py follow the Windows filename
    convention in terms of the directory separator, and this is causing
    trouble when the build environment is cygwin (while the compiler
    and Python are MinGW).  We could have fixed that in the configure
    script, but it felt simpler to do so in python-config.py

gdb/ChangeLog:

        * configure.ac: Add handling of Python distribution on Windows.
        * python-config.py: If the LIBS, SYSLIBS, LIBPL and/or LINKFORSHARED
        sysconfig variables are not defined, then do not use them.
        On Windows, if LIBPL is not defined, then use prefix + '/libs'
        instead.  On Windows, return all paths using forward-slashes
        rather than backslashes.

1 files changed, 27 insertions, 7 deletions

diff --git a/gdb/python/python-config.py b/gdb/python/python-config.py
index 0230eb4925c..75ed2d2183e 100644
--- a/gdb/python/python-config.py
+++ b/gdb/python/python-config.py
@@ -30,28 +30,48 @@ opt_flags = [flag for (flag, val) in opts]
 if '--help' in opt_flags:
     exit_with_usage(code=0)
 
+def to_unix_path(path):
+    """On Windows, returns the given path with all backslashes
+    converted into forward slashes.  This is to help prevent problems
+    when using the paths returned by this script with cygwin tools.
+    In particular, cygwin bash treats backslashes as a special character.
+
+    On Unix systems, returns the path unchanged.
+    """
+    if os.name == 'nt':
+        path = path.replace('\\', '/')
+    return path
+
 for opt in opt_flags:
     if opt == '--prefix':
-        print sysconfig.PREFIX
+        print to_unix_path(sysconfig.PREFIX)
 
     elif opt == '--exec-prefix':
-        print sysconfig.EXEC_PREFIX
+        print to_unix_path(sysconfig.EXEC_PREFIX)
 
     elif opt in ('--includes', '--cflags'):
         flags = ['-I' + sysconfig.get_python_inc(),
                  '-I' + sysconfig.get_python_inc(plat_specific=True)]
         if opt == '--cflags':
             flags.extend(getvar('CFLAGS').split())
-        print ' '.join(flags)
+        print to_unix_path(' '.join(flags))
 
     elif opt in ('--libs', '--ldflags'):
-        libs = getvar('LIBS').split() + getvar('SYSLIBS').split()
+        libs = []
+        if getvar('LIBS') is not None:
+            libs.extend(getvar('LIBS').split())
+        if getvar('SYSLIBS') is not None:
+            libs.extend(getvar('SYSLIBS').split())
         libs.append('-lpython'+pyver)
         # add the prefix/lib/pythonX.Y/config dir, but only if there is no
         # shared library in prefix/lib/.
         if opt == '--ldflags':
             if not getvar('Py_ENABLE_SHARED'):
-                libs.insert(0, '-L' + getvar('LIBPL'))
-            libs.extend(getvar('LINKFORSHARED').split())
-        print ' '.join(libs)
+                if getvar('LIBPL') is not None:
+                    libs.insert(0, '-L' + getvar('LIBPL'))
+                elif os.name == 'nt':
+                    libs.insert(0, '-L' + sysconfig.PREFIX + '/libs')
+            if getvar('LINKFORSHARED') is not None:
+                libs.extend(getvar('LINKFORSHARED').split())
+        print to_unix_path(' '.join(libs))