Boost 无序地图漂亮打印机正在多次打印值以及不需要的值

Posted 2023-02-17

【中文标题】Boost 无序地图漂亮打印机正在多次打印值以及不需要的值

【英文标题】：Boost unordered map pretty printer is printing value multiple times along with unwanted values

【发布时间】：2014-03-20 14:10:34

【问题描述】：

我正在尝试通过从此处向现有的 boost 漂亮打印机列表添加一个新打印机来为 boost::unordered_map 添加一个漂亮的打印机： https://sourceware.org/gdb/wiki/STLSupporthttps://github.com/ruediger/Boost-Pretty-Printer

但是，当我尝试打印我的地图时，会多次打印很多值和一些不需要的字符。我不确定应该对我现有的代码进行哪些修改以使其仅打印一次值，而没有任何不需要的字符。这是我在 myMap.cpp 中更新 myMap 的循环：

 for (int i=0; i<=10; i++)
 
 string s = to_string(i);
 myMap[s] = i;
 

当我在 gdb 中将 myMap 打印为

(gdb)p myMap 

我得到如下结果：

$1 = boost::unordered::detail = "1" = 1, "0" = 0, "2" = 2, "1" = 1, "0" = 0, "3" = 3, 
"2" = 2, "1" = 1, "0" = 0, "4" = 4, "3" = 3, "2" = 2, "1" = 1, "0" = 0, "5" = 5, "4" = 4, 
"3" = 3, "2" = 2, "1" = 1, "0" = 0, "6" = 6, "5" = 5, "4" = 4, "3" = 3, "2" = 2, "1" = 1, 
 "0" = 0, "7" = 7, "10" = 10, "6" = 6, "5" = 5, "4" = 4, "3" = 3, "2" = 2, "1" = 1, 
"0" = 0, "8" = 8, "7" = 7, "10" = 10, "6" = 6, "5" = 5, "4" = 4, "3" = 3, "2" = 2, 
"1" = 1, "0" = 0, "9" = 9, "8" = 8, "7" = 7, "10" = 10, "6" = 6, "5" = 5, "4" = 4, 
"3" = 3, "2" = 2, "1" = 1, "0" = 0, 
" \204`", '\000' <repeats 13 times>, "\321\n\002", '\000' <repeats 181 times>... = 0, 
"9" = 9, "8" = 8, "7" = 7, "10" = 10, "6" = 6, "5" = 5, "4" = 4, "3" = 3, "2" = 2, 
"1" = 1, "0" = 0

我的漂亮打印机的 python 代码如下所示：

@_register_printer
class BoostUnorderedMap:
"Pretty Printer for boost::unordered_map"
printer_name = 'boost::unordered_map'
version = '1.40'
type_name_re = '^boost::unordered::unordered_map<.*>$'

class _iterator:
def __init__(self,fields):
   type_1 = fields.val.type.template_argument(0)
   type_2 = fields.val.type.template_argument(1)

   self.buckets = fields.val['table_']['buckets_']
   self.bucket_count = fields.val['table_']['bucket_count_']
   self.bucket_size = fields.val['table_']['size_']
   self.current_bucket = 0
   self.value = 0
   self.iteration = 0
   self.temp_node = 0
   self.bucket_to_start = 0
   pair = "std::pair<%s const, %s>" % (type_1, type_2)
   self.pair_pointer = gdb.lookup_type(pair).pointer()
   self.base_pointer = gdb.lookup_type("boost::unordered::detail::value_base< %s >" % pair).pointer()
   self.node_pointer = gdb.lookup_type("boost::unordered::detail::ptr_node<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, int> >").pointer()
   self.node = self.buckets[self.current_bucket]['next_']



def __iter__(self):
    return self

def next(self): 
    while not self.node:
            self.current_bucket = self.current_bucket + 1
            if self.current_bucket >= self.bucket_count:
                raise StopIteration
            self.node = self.buckets[self.current_bucket]['next_']

    iterator = self.node.cast(self.node_pointer).cast(self.base_pointer).cast(self.pair_pointer).dereference()   
        self.node = self.node['next_']

        return ('%s' % iterator['first'], iterator['second'])

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

def children(self):
return self._iterator(self)

def to_string(self):
return "boost::unordered::detail"

任何帮助将不胜感激。

【参考方案1】：

如果不了解有关 Boost 内部结构的更多信息，很难确切知道出了什么问题。如果是我，我可能会破解“下一个”方法来添加一些调试打印，看看出了什么问题。

无论如何，在您的 Python 代码中有一件事很突出。现在您正在返回这样的子元素：

    return ('%s' % iterator['first'], iterator['second'])

但是，使用此 API 的常用方法是将地图的键和值作为单独的子项返回，然后使用 display_hint 方法返回“地图”。见

https://sourceware.org/gdb/onlinedocs/gdb/Pretty-Printing-API.html

您可以在下一个方法中使用“yield”轻松完成此操作。