[英]GDB-Python scripting: any samples iterating through C/C++ struct fields
The new GDB-Python scripting API looks quite powerful and should be very useful. 新的GDB-Python脚本API看起来非常强大,应该非常有用。 However writing a useful script to iterate through the fields in a struct of C or C++ is not trivial.
但是,编写一个有用的脚本来迭代C或C ++结构中的字段并非易事。 Does any one know some solid samples that does exactly that?
有没有人知道一些确切的样品呢?
Thanks in advance. 提前致谢。
Update the final sample: Replace the _print_fields()
in early sample. 更新最终样本:替换早期样本中的
_print_fields()
。
if l.type.code == gdb.TYPE_CODE_STRUCT:
print "Found a struct %s " % n
#self._print_fields(n, t)
self._print_deep_items(n, t, l)
else:
print "Found no struct"
def _print_deep_items (self, n_, type_, instance_):
for fld in type_.fields():
fn = fld.name
ft = fld.type
fv = instance_[fn]
if fv.type.code == gdb.TYPE_CODE_STRUCT:
print " Found a sub struct %s " % fn
self._print_deep_items(fn, ft, fv)
else:
print " Field %s " % fn, " type %s " % ft.tag, " value %s " % fv
And the output: 并输出:
variable s1 type S1
Found a struct s1
Field v1 type None value 0
Field v2 type None value 0
Found a sub struct v3
Field w3 type None value 0
Update with the first sample: Got the following sample code working. 使用第一个示例进行更新:获得以下示例代码。 This is not the optimal as it does a look-up on every field after composing the string field name.
这不是最佳的,因为它在组成字符串字段名称后在每个字段上进行查找。 abarnert is showing a promising and elegant approach, the working code is updated in the above final update section.
abarnert正在展示一种有前途和优雅的方法,工作代码在上面的最终更新部分进行了更新。
import gdb
class PrintGList(gdb.Command):
"""print fields of a struct: wzd struct_object
Iterate through the fields of a struct, and display
a human-readable form of the objects."""
def __init__(self):
gdb.Command.__init__(self, "wzd", gdb.COMMAND_DATA, gdb.COMPLETE_SYMBOL, True)
def invoke(self, arg, from_tty):
arg_list = gdb.string_to_argv(arg)
if len(arg_list) < 1:
print "usage: wzd struct"
return
n = arg_list[0]
l = gdb.parse_and_eval(arg_list[0])
m = l.type.tag
print " variable %s " % n, " type %s " % m
try:
t = gdb.lookup_type(m)
except RuntimeError, e:
print "type %s not found" % t
return
if l.type.code == gdb.TYPE_CODE_STRUCT:
print "Found a struct %s " % n
self._print_fields(n, t)
else:
print "Found no struct"
def _print_fields(self, n, typeobject):
print typeobject
flds = typeobject.fields()
for x in flds:
sn = n + "." + x.name
print " field %s" % sn, " code %s " % x.type.code, " type %s " % x.type.tag
if x.type.code == gdb.TYPE_CODE_STRUCT:
print "Found sub level struct %s " % sn
sl = gdb.parse_and_eval(sn)
sm = sl.type.tag
st = gdb.lookup_type( sm )
self._print_fields(sn, x.type)
def _deep_items (self, type_):
for k, v in type_.iteritems():
if k:
print " k v %s " % k , " %s " % v
else:
print " v ", " %s " % v
PrintGList()
The source file to test with: 要测试的源文件:
struct S2 { int w3; };
struct S1 { int v1, v2; struct S2 v3; } s1;
int main(int argc, char *argv[]) { return 0; }
Example output: 示例输出:
variable s1 type S1
Found a struct s1
S1
field s1.v1 typecode 8 type None
field s1.v2 typecode 8 type None
field s1.v3 typecode 3 type S2
Found sub level struct s1.v3
S2
field s1.v3.w3 typecode 8 type None
GDB session to get the: source /home/me/testpath/wzdfile.py file a.out b main r wzd s1 quit GDB会话获取:source /home/me/testpath/wzdfile.py文件a.out b main r wzd s1 quit
According to the docs , iterating through the fields of a C struct should be pretty trivial: 根据文档 ,迭代C结构的字段应该是非常简单的:
If the type is a structure or class type, or an enum type, the fields of that type can be accessed using the Python dictionary syntax.
如果类型是结构或类类型或枚举类型,则可以使用Python字典语法访问该类型的字段。 For example, if
some_type
is agdb.Type
instance holding a structure type, you can access its foo field with:例如,如果
some_type
是包含结构类型的gdb.Type
实例,则可以使用以下命令访问其foo字段:bar = some_type['foo']
bar
will be agdb.Field
object;bar
将是一个gdb.Field
对象; see below under the description of theType.fields
method for a description of thegdb.Field
class.有关
gdb.Field
类的说明,请参阅下面的Type.fields
方法的说明。
You can also use Type.fields
to get the fields of a struct
explicitly, but (as of 7.4) you can just use the normal dict
methods as well, so to get a list of name/ Field
pairs: 您也可以使用
Type.fields
显式获取struct
的字段,但是(从7.4开始)您也可以使用普通的dict
方法,以获取名称/ Field
对的列表:
for name, field in foo.type.iteritems():
Or, for just the names: 或者,仅为名称:
for name, field in foo.type.iterkeys():
And so on. 等等。
This doesn't seem to be directly documented on that page, but gdb.types implies it pretty strongly when it says that deep_items
: 这似乎没有在该页面上直接记录,但gdb.types在它表示
deep_items
时非常强烈地暗示它:
Returns a Python iterator similar to the standard gdb.Type.iteritems method.
返回类似于标准gdb.Type.iteritems方法的Python迭代器。
For example, given this C type: 例如,给定此C类型:
struct S {
int x;
int y;
};
You can do this: 你可以这样做:
(gdb) python struct_S = my_s.type # or gdb.lookup_type("struct S"), etc.
(gdb) python print struct_S.keys()
{['a', 'b']}
(gdb) python print my_s['a']
0
From a quick glance at the types.py
source , look at how gdb.types.deep_item(type_)
is implemented, and that does seem to be all there is to it. 快速浏览一下
types.py
源代码 ,看看如何实现gdb.types.deep_item(type_)
,这似乎就是它的全部内容。
Before gdb 7.4, you could not treat a type directly as a dict
. 在gdb 7.4之前,您无法直接将类型视为
dict
。 That is, no for name in instance_.type:
or instance_.type.iteritems()
, etc. You had to explicitly call fields
. 也就是说,
for name in instance_.type:
或instance_.type.iteritems()
等中没有for name in instance_.type:
。您必须显式调用fields
。 Anyway, putting it all together, here's a simple example for iterating over all of the fields of a structure with gdb 7.2: 无论如何,将它们放在一起,这是一个用gdb 7.2迭代结构的所有字段的简单示例:
for field in inst.fields:
fname = field.name
ftype = field.type
fval = inst[fname]
Except that this won't work if your struct
has an anonymous struct
inside it. 除非你的
struct
有一个匿名struct
,否则这将不起作用。 For that, you'll need deep_items
(and, if that isn't there in 7.2, you'll need to look at the code and figure out how to implement it yourself). 为此,你需要
deep_items
(如果在7.2中不存在,你需要查看代码并找出如何自己实现它)。
So, not quite trivial in 7.2, but pretty simple. 所以,在7.2中并不是那么简单,但非常简单。 And, if you want trivial, just upgrade to 7.4.
而且,如果你想要琐碎,只需升级到7.4。
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