[RFA 2/2] allow building GDB with Python support on MinGW

[Joel Brobecker <brobecker@adacore.com>]

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.

Tested on x86_64-linux.  Python gets sucessfully built in MinGW/GDB,
and simple Python commands seem to work.

---
 gdb/configure               |   17 ++++++++++++-----
 gdb/configure.ac            |   17 ++++++++++++-----
 gdb/python/python-config.py |   34 +++++++++++++++++++++++++++-------
 3 files changed, 51 insertions(+), 17 deletions(-)

diff --git a/gdb/configure b/gdb/configure
index 2540f8b..5a6d0be 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -10478,6 +10478,13 @@ else
       # Assume the python binary is ${with_python}/bin/python.
       python_prog="${with_python}/bin/python"
       python_prefix=
+      # If python does not exit ${with_python}/bin, then try in
+      # ${with_python}.  On Windows/MinGW, this is where the Python
+      # executable is.
+      if test ! -x "${python_prog}"; then
+        python_prog="${with_python}/python"
+        python_prefix=
+      fi
       if test ! -x "${python_prog}"; then
         # Fall back to gdb 7.0/7.1 behaviour.
         python_prog=missing
@@ -10652,7 +10659,7 @@ fi
   have_libpython=no
   if test "${have_python_config}" = yes; then
     python_version=`echo " ${python_libs} " \
-                         | sed -e 's,^.* -l\(python[0-9]*[.][0-9]*\) .*$,\1,'`
+                         | sed -e 's,^.* -l\(python[0-9]*[.]\?[0-9]*\).*$,\1,'`
     case "${python_version}" in
     python*)
 
@@ -10850,19 +10857,19 @@ $as_echo "${found_usable_python}" >&6; }
 
     fi
   fi
-  if test "${have_libpython}" = python2.7; then
+  if test "${have_libpython}" = python2.7 -o "${have_libpython}" = python27; then
 
 $as_echo "#define HAVE_LIBPYTHON2_7 1" >>confdefs.h
 
-  elif test "${have_libpython}" = python2.6; then
+  elif test "${have_libpython}" = python2.6 -o "${have_libpython}" = python26; then
 
 $as_echo "#define HAVE_LIBPYTHON2_6 1" >>confdefs.h
 
-  elif test "${have_libpython}" = python2.5; then
+  elif test "${have_libpython}" = python2.5 -o "${have_libpython}" = python25; then
 
 $as_echo "#define HAVE_LIBPYTHON2_5 1" >>confdefs.h
 
-  elif test "${have_libpython}" = python2.4; then
+  elif test "${have_libpython}" = python2.4 -o "${have_libpython}" = python24; then
 
 $as_echo "#define HAVE_LIBPYTHON2_4 1" >>confdefs.h
 
diff --git a/gdb/configure.ac b/gdb/configure.ac
index afb7314..68b0838 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -669,6 +669,13 @@ else
       # Assume the python binary is ${with_python}/bin/python.
       python_prog="${with_python}/bin/python"
       python_prefix=
+      # If python does not exit ${with_python}/bin, then try in
+      # ${with_python}.  On Windows/MinGW, this is where the Python
+      # executable is.
+      if test ! -x "${python_prog}"; then
+        python_prog="${with_python}/python"
+        python_prefix=
+      fi
       if test ! -x "${python_prog}"; then
         # Fall back to gdb 7.0/7.1 behaviour.
         python_prog=missing
@@ -763,7 +770,7 @@ else
   have_libpython=no
   if test "${have_python_config}" = yes; then
     python_version=`echo " ${python_libs} " \
-                         | sed -e 's,^.* -l\(python[[0-9]]*[[.]][[0-9]]*\) .*$,\1,'`
+                         | sed -e 's,^.* -l\(python[[0-9]]*[[.]]\?[[0-9]]*\).*$,\1,'`
     case "${python_version}" in
     python*)
       AC_TRY_LIBPYTHON(${python_version}, have_libpython,
@@ -791,13 +798,13 @@ else
                        ${python_includes}, "${python_libs} -lpython2.4")
     fi
   fi
-  if test "${have_libpython}" = python2.7; then
+  if test "${have_libpython}" = python2.7 -o "${have_libpython}" = python27; then
     AC_DEFINE(HAVE_LIBPYTHON2_7, 1, [Define if Python 2.7 is being used.])
-  elif test "${have_libpython}" = python2.6; then
+  elif test "${have_libpython}" = python2.6 -o "${have_libpython}" = python26; then
     AC_DEFINE(HAVE_LIBPYTHON2_6, 1, [Define if Python 2.6 is being used.])
-  elif test "${have_libpython}" = python2.5; then
+  elif test "${have_libpython}" = python2.5 -o "${have_libpython}" = python25; then
     AC_DEFINE(HAVE_LIBPYTHON2_5, 1, [Define if Python 2.5 is being used.])
-  elif test "${have_libpython}" = python2.4; then
+  elif test "${have_libpython}" = python2.4 -o "${have_libpython}" = python24; then
     AC_DEFINE(HAVE_LIBPYTHON2_4, 1, [Define if Python 2.4 is being used.])
   fi
 
diff --git a/gdb/python/python-config.py b/gdb/python/python-config.py
index 0230eb4..75ed2d2 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))
 
-- 
1.7.1