mozilla-central modules for debugger detection

Borrows two python modules from mozilla-central to give mach the ability
to detect and pass arguments to a system's preferred debugger.

Links to borrowed files:
http://hg.mozilla.org/mozilla-central/file/c9cfa9b91dea/testing/mozbase/mozinfo/mozinfo/mozinfo.py
http://hg.mozilla.org/mozilla-central/file/c9cfa9b91dea/testing/mozbase/mozdebug/mozdebug/mozdebug.py

python/mozdebug/mozdebug.py

@@ -0,0 +1,168 @@
+#!/usr/bin/env python
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import mozinfo
+from collections import namedtuple
+from distutils.spawn import find_executable
+
+__all__ = ['get_debugger_info',
+           'get_default_debugger_name',
+           'DebuggerSearch']
+
+'''
+Map of debugging programs to information about them, like default arguments
+and whether or not they are interactive.
+
+To add support for a new debugger, simply add the relative entry in
+_DEBUGGER_INFO and optionally update the _DEBUGGER_PRIORITIES.
+'''
+_DEBUGGER_INFO = {
+    # gdb requires that you supply the '--args' flag in order to pass arguments
+    # after the executable name to the executable.
+    'gdb': {
+        'interactive': True,
+        'args': ['-q', '--args']
+    },
+
+    'cgdb': {
+        'interactive': True,
+        'args': ['-q', '--args']
+    },
+
+    'lldb': {
+        'interactive': True,
+        'args': ['--'],
+        'requiresEscapedArgs': True
+    },
+
+    # Visual Studio Debugger Support.
+    'devenv.exe': {
+        'interactive': True,
+        'args': ['-debugexe']
+    },
+
+    # Visual C++ Express Debugger Support.
+    'wdexpress.exe': {
+        'interactive': True,
+        'args': ['-debugexe']
+    },
+
+    # valgrind doesn't explain much about leaks unless you set the
+    # '--leak-check=full' flag. But there are a lot of objects that are
+    # semi-deliberately leaked, so we set '--show-possibly-lost=no' to avoid
+    # uninteresting output from those objects. We set '--smc-check==all-non-file'
+    # and '--vex-iropt-register-updates=allregs-at-mem-access' so that valgrind
+    # deals properly with JIT'd JavaScript code.
+    'valgrind': {
+        'interactive': False,
+        'args': ['--leak-check=full',
+                '--show-possibly-lost=no',
+                '--smc-check=all-non-file',
+                '--vex-iropt-register-updates=allregs-at-mem-access']
+    }
+}
+
+# Maps each OS platform to the preferred debugger programs found in _DEBUGGER_INFO.
+_DEBUGGER_PRIORITIES = {
+      'win': ['devenv.exe', 'wdexpress.exe'],
+      'linux': ['gdb', 'cgdb', 'lldb'],
+      'mac': ['lldb', 'gdb'],
+      'unknown': ['gdb']
+}
+
+def get_debugger_info(debugger, debuggerArgs = None, debuggerInteractive = False):
+    '''
+    Get the information about the requested debugger.
+
+    Returns a dictionary containing the |path| of the debugger executable,
+    if it will run in |interactive| mode, its arguments and whether it needs
+    to escape arguments it passes to the debugged program (|requiresEscapedArgs|).
+    If the debugger cannot be found in the system, returns |None|.
+
+    :param debugger: The name of the debugger.
+    :param debuggerArgs: If specified, it's the arguments to pass to the debugger,
+    as a string. Any debugger-specific separator arguments are appended after these
+    arguments.
+    :param debuggerInteractive: If specified, forces the debugger to be interactive.
+    '''
+
+    debuggerPath = None
+
+    if debugger:
+        # Append '.exe' to the debugger on Windows if it's not present,
+        # so things like '--debugger=devenv' work.
+        if (os.name == 'nt'
+            and not debugger.lower().endswith('.exe')):
+            debugger += '.exe'
+
+        debuggerPath = find_executable(debugger)
+
+    if not debuggerPath:
+        print 'Error: Could not find debugger %s.' % debugger
+        return None
+
+    debuggerName = os.path.basename(debuggerPath).lower()
+
+    def get_debugger_info(type, default):
+        if debuggerName in _DEBUGGER_INFO and type in _DEBUGGER_INFO[debuggerName]:
+            return _DEBUGGER_INFO[debuggerName][type]
+        return default
+
+    # Define a namedtuple to access the debugger information from the outside world.
+    DebuggerInfo = namedtuple(
+        'DebuggerInfo',
+        ['path', 'interactive', 'args', 'requiresEscapedArgs']
+    )
+
+    debugger_arguments = []
+
+    if debuggerArgs:
+        # Append the provided debugger arguments at the end of the arguments list.
+        debugger_arguments += debuggerArgs.split()
+
+    debugger_arguments += get_debugger_info('args', [])
+
+    # Override the default debugger interactive mode if needed.
+    debugger_interactive = get_debugger_info('interactive', False)
+    if debuggerInteractive:
+        debugger_interactive = debuggerInteractive
+
+    d = DebuggerInfo(
+        debuggerPath,
+        debugger_interactive,
+        debugger_arguments,
+        get_debugger_info('requiresEscapedArgs', False)
+    )
+
+    return d
+
+# Defines the search policies to use in get_default_debugger_name.
+class DebuggerSearch:
+  OnlyFirst = 1
+  KeepLooking = 2
+
+def get_default_debugger_name(search=DebuggerSearch.OnlyFirst):
+    '''
+    Get the debugger name for the default debugger on current platform.
+
+    :param search: If specified, stops looking for the debugger if the
+     default one is not found (|DebuggerSearch.OnlyFirst|) or keeps
+     looking for other compatible debuggers (|DebuggerSearch.KeepLooking|).
+    '''
+
+    # Find out which debuggers are preferred for use on this platform.
+    debuggerPriorities = _DEBUGGER_PRIORITIES[mozinfo.os if mozinfo.os in _DEBUGGER_PRIORITIES else 'unknown']
+
+    # Finally get the debugger information.
+    for debuggerName in debuggerPriorities:
+        debuggerPath = find_executable(debuggerName)
+        if debuggerPath:
+            return debuggerName
+        elif not search == DebuggerSearch.KeepLooking:
+            return None
+
+    return None