Re: issue with GDB python pretty-printers for libstdc++

[Paul Smith]

On Wed, 2020-02-26 at 17:23 +0000, Jonathan Wakely wrote:
> I compiled this program:
> 
> #include <unordered_map>
> 
> int main()
> {
>   std::unordered_map<int, int> m;
>   m[3] = 5;
>   return m[1];
> }
> 
> And with Fedora 31's GDB 8.3.50 I get this behaviour:

I can't reproduce with a simple test either.  But in my full system I
have something like this:

  class Obj {
    typedef uint64_t GroupId;
    typedef uint64_t ObjectId;
    typedef std::unordered_map<GroupId, ObjectId> GroupIdToObjectIdMap;

    GroupIdToObjectIdMap objMap;
  };

then in GDB I do this:

  (gdb) ptype $v->objMap
  type = std::unordered_map<unsigned long, unsigned long>

Fine, but then when I do this:

  (gdb) py v = gdb.parse_and_eval('$v')
  (gdb) py print str(v.type)
  Obj::GroupIdToObjectIdMap

OK, but then when I do this:

  (gdb) py print str(v.type.strip_typedefs())
  class std::unordered_map<unsigned long, unsigned long, std::hash<unsigned 
long>, std::equal_to<unsigned long>, std::allocator<std::pair<unsigned long 
const, unsigned long> > >

Note the "class " prefix here.  And:

  (gdb) py t = gdb.lookup_type(str(v.type.strip_typedefs())
Traceback (most recent call last):
    File "<string>", line 1, in <module>
  gdb.error: No type named class std::unordered_map<unsigned long, unsigned 
long, std::hash<unsigned long>, std::equal_to<unsigned long>, 
std::allocator<std::pair<unsigned long const, unsigned long> > >::__node_type.
  Error while executing Python code.

If I use v.type.strip_typedefs().name it works.

I haven't been able to reproduce this in a small separate test case.  I
have no idea what the difference is :(


Thanks!!