gdb PrettyPrinter插件例程StdStringPrinter在处理std:：basic\u string<wchar\u t（，.*）时崩溃？>$

Question

我在分析一个崩溃转储，其中我实现了Python插件pretty-printer（“/usr/share/gdb/Python/libstdcxx/v6）/打印机.py）在以下行中崩溃

return self.val['_M_dataplus']['_M_p'].string (encoding, length = len)
LookupError: unknown encoding: UCS-4

如下图所示

^{pr2}$

我开始分析代码

class StdStringPrinter:
    "Print a std::basic_string of some kind"

    def __init__(self, encoding, val):
        self.encoding = encoding
        self.val = val

    def to_string(self):
        # Look up the target encoding as late as possible.
        encoding = self.encoding
        if encoding == 0:
            encoding = gdb.parameter('target-charset')
        elif encoding == 1:
            encoding = gdb.parameter('target-wide-charset')

        # Make sure &string works, too.
        type = self.val.type
        if type.code == gdb.TYPE_CODE_REF:
            type = type.target ()

        # Calculate the length of the string so that to_string returns
        # the string according to length, not according to first null
        # encountered.
        ptr = self.val ['_M_dataplus']['_M_p']
        realtype = type.unqualified ().strip_typedefs ()
        reptype = gdb.lookup_type (str (realtype) + '::_Rep').pointer ()
        header = ptr.cast(reptype) - 1
        len = header.dereference ()['_M_length']
        return self.val['_M_dataplus']['_M_p'].string (encoding, length = len)

并意识到有一个用参数['gdb.parameter', 'gdb.parameter']调用gdb.parameter，它返回

(gdb) python print gdb.parameter('target-wide-charset')
UCS-4
(gdb) python print gdb.parameter('target-charset')
ANSI_X3.4-1968

编码被传递给self.val['_M_dataplus']['_M_p'].string (encoding, length = len)，我的最佳猜测是，它调用str.encode或{}，但它们都不是{a1}UCS-4。在

>>> u'data'.encode('UCS-4')

Traceback (most recent call last):
  File "<pyshell#529>", line 1, in <module>
    u'data'.encode('UCS-4')
LookupError: unknown encoding: UCS-4

我强烈地感觉到这是一个错误，有什么线索或想法吗？在

Answer 1

这取决于Python是如何构建的。您可以从gdb执行此操作以了解：

python import sys
python print sys.maxunicode

我以前没见过这个版本；我想大多数发行版都是用UCS-4支持构建的。在

同样值得考虑的是，您的系统中有哪些wchar_t。也许UCS-4也错了。您可以在gdb中使用“settargetwidecharset”来更改这一点。一般情况下，gdb不可能猜出正确的值。在