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问题:
I have a struct in GDB and want to run a script which examines this struct. In Python GDB you can easily access the struct via
(gdb) python mystruct = gdb.parse_and_eval("mystruct")
Now I got this variable called mystruct which is a GDB.Value object. And I can access all the members of the struct by simply using this object as a dictionary (likemystruct['member']).
The problem is, that my script doesn't know which members a certain struct has. So I wanted to get the keys (or even the values) from this GDB.Value object. But neither mystruct.values() nor mystruct.keys() is working here.
Is there no possibility to access this information? I think it's highly unlikely that you can't access this information, but I didn't found it anywhere. A dir(mystruct) showed me that there also is no keys or values function. I can see all the members by printing the mystruct, but isn't there a way to get the members in python?
回答1:
From GDB documentation:
You can get the type of mystruct like so:
tp = mystruct.type
and iterate over the fields via tp.fields()
No evil workarounds required ;-)
Update: GDB 7.4 has just been released. From the announcement:
Type objects for struct and union types now allow access to the fields using standard Python dictionary (mapping) methods.
回答2:
Evil workaround:
python print eval("dict(" + str(mystruct)[1:-2] + ")")
I don't know if this is generalisable. As a demo, I wrote a minimal example test.cpp
#include <iostream> struct mystruct { int i; double x; } mystruct_1; int main () { mystruct_1.i = 2; mystruct_1.x = 1.242; std::cout << "Blarz"; std::cout << std::endl; }
Now I run g++ -g test.cpp -o test as usual and fire up gdb test. Here is a example session transcript:
(gdb) break main Breakpoint 1 at 0x400898: file test.cpp, line 11. (gdb) run Starting program: ... Breakpoint 1, main () at test.cpp:11 11 mystruct_1.i = 2; (gdb) step 12 mystruct_1.x = 1.242; (gdb) step 13 std::cout << "Blarz"; (gdb) python mystruct = gdb.parse_and_eval("mystruct_1") (gdb) python print mystruct {i = 2, x = 1.242} (gdb) python print eval("dict(" + str(mystruct)[1:-2] + ")") {'i': 2, 'x': 1.24} (gdb) python print eval("dict(" + str(mystruct)[1:-2] + ")").keys() ['i', 'x']
