Question

I had to delete some of the entries from c++ std::map, for that purpose I iterate over the std::map and used erase. But I get an error. The error is like :

0x0017f3f6 in std::_Rb_tree_rebalance_for_erase () from /usr/local/lib/libstdc++.so.6
(gdb) bt
#0  0x0017f3f6 in std::_Rb_tree_rebalance_for_erase () from /usr/local/lib/libstdc++.so.6
#1  0x00487ef4 in getLetters () from /usr/lib/libmail.so
#2  0x0048cacc in getHeader () from /usr/lib/libmail.so

#6  0x08048802 in __gxx_personality_v0 ()
#7  0x00251e9c in __libc_start_main () from /lib/libc.so.6
#8  0x080486a1 in __gxx_personality_v0 ()
(gdb)

The code was something like this:

int nlsize=LettersMap.size();

if(nlsize > MAXNL)              
{                               
        std::map <std::string,MSG_HEADER>::iterator it;
        int i=0;                
        for( i=0, it=LettersMap.begin();  i <nlsize-MAXNL  ;i++, it++)
        {                       
                LettersMap.erase(it);                 
        }                       
}   

Can someone please point out the error

Answer 1

int n = nlsize - MAXNL;
while (n-- > 0) {
    LettersMap.erase(LettersMap.begin());
}

The iterator it is becoming instable by erase.