Re: [Dev-C++] STL Map question

[Shane B. <ast...@te...>]

MessageYes, I appologize for not including the header definition.  Here =
it is.

#ifndef USERLIST_H
#define USERLIST_H
  =20
#include <map.h>
  =20
class User;
   =20
class UserList {
public:
struct ltstr
{
  bool operator()(const char* s1, const char* s2) const
  {
    return strcmp(s1, s2) < 0;
  }
};
    typedef std::map<const char *, User *, ltstr> UserMap;
 =20
    UserList();
    ~UserList();
=20
    void AddUser(User *pUser);
    bool DeleteUser(const char *pNick);
    User *FindUser(const char *pNick);
    unsigned long Length();
 =20
    UserMap m_mapUsers;
};
   =20
   =20
#endif

    -Shane

  ----- Original Message -----=20
  From: Ioannis Vranos=20
  To: 'C++'=20
  Sent: Wednesday, July 09, 2003 4:41 PM
  Subject: RE: [Dev-C++] STL Map question


  -----Original Message-----
  From: dev...@li... =
[mailto:dev...@li...] On Behalf Of Shane =
Bryldt
  Sent: Thursday, July 10, 2003 12:54 AM
  To: C++
  Subject: [Dev-C++] STL Map question


    Hello,

        I recently ran into an issue that I can't seem to pinpoint the =
cause of.  99% of the time, it seems to work, so it seems to be a small =
situational bug.  Subject, is a UserList class, which internally =
implements an STL map.  I am not sure why, but it seems to crash =
occasionally when I attempt to call the map::find function, with a valid =
null terminated char array.  The map template implements a simple case =
insensative comparison.  As I said, it works more often than not, but =
for some reason when attempting to delete from the list sometimes, it =
causes a SEGFAULT.  Here is what GDB has to say:

    Program received signal SIGSEGV, Segmentation fault.
    0x80bb142 in _Rb_tree<char const *, pair<char const *const, User *>, =
_Select1st<pair<char const *const, User *> >, UserList::ltstr, =
allocator<User *> >::find (
        this=3D0xbf14b30, __k=3D@0xbfbff7bc) at =
/usr/include/g++/stl_tree.h:1118
    1118      _Link_type __x =3D _M_root();      // Current node.=20
    (gdb) up
    #1  0x80bb529 in map<char const *, User *, UserList::ltstr, =
allocator<User *> >::find (this=3D0xbf14b30, __x=3D@0xbfbff7bc) at =
/usr/include/g++/stl_map.h:187
    187       iterator find(const key_type& __x) { return =
_M_t.find(__x); }
    (gdb) up
    #2  0x80ba8e9 in UserList::DeleteUser (this=3D0xbf14b30,=20
        pNick=3D0xbf12300 "_=C7=E1=DF=D1=D2_") at UserList.cpp:26
    26              UserMap::iterator it =3D m_mapUsers.find(pNick);
    (gdb) print pNick
    $1 =3D 0xbf12300 "_=C7=E1=DF=D1=D2_"


    And here is the code in question.

    bool UserList::DeleteUser(const char *pNick)
    {
        bool bRet =3D false;
    =20
        if(m_mapUsers.size() > 0)
        {
            UserMap::iterator it =3D m_mapUsers.find(pNick);
            if(it !=3D m_mapUsers.end())
            {
                m_mapUsers.erase(it);
                bRet =3D true;
            }
        }

        return bRet;
    }


    My first thought was that the MAP container had issues when =
attempting to "find" with 0 elements, but that didn't seem to affect =
anything.  Any thoughts?=20

  Are you sure that m_mapUsers is an object of type UserMap and UserMap =
is a typedef of a map type?






  Ioannis Vranos

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