c++ - I get this error: "glibc detected"

Question

I just wrote a piece of CPP code and I compiled it using G++ in ubuntu. When I run my code everything is fine, the code runs well and gives output but doesn't exit and it gives this error:

 *** glibc detected *** ./a.out: free(): invalid next size (fast): 0x09f931f0 ***
======= Backtrace: =========
/lib/libc.so.6(+0x6c501)[0x3de501]
/lib/libc.so.6(+0x6dd70)[0x3dfd70]
/lib/libc.so.6(cfree+0x6d)[0x3e2e5d]
/usr/lib/libstdc++.so.6(_ZdlPv+0x21)[0x6e2441]
./a.out[0x8049ce6]
/lib/libc.so.6(+0x2f69e)[0x3a169e]
/lib/libc.so.6(+0x2f70f)[0x3a170f]
/lib/libc.so.6(__libc_start_main+0xef)[0x388cef]
./a.out[0x8048a61]
======= Memory map: ========
00219000-0021a000 r-xp 00000000 00:00 0          [vdso]
00354000-00370000 r-xp 00000000 08:01 8781845    /lib/ld-2.12.1.so
00370000-00371000 r--p 0001b000 08:01 8781845    /lib/ld-2.12.1.so
00371000-00372000 rw-p 0001c000 08:01 8781845    /lib/ld-2.12.1.so
00372000-004c9000 r-xp 00000000 08:01 8781869    /lib/libc-2.12.1.so
004c9000-004ca000 ---p 00157000 08:01 8781869    /lib/libc-2.12.1.so
004ca000-004cc000 r--p 00157000 08:01 8781869    /lib/libc-2.12.1.so
004cc000-004cd000 rw-p 00159000 08:01 8781869    /lib/libc-2.12.1.so
004cd000-004d0000 rw-p 00000000 00:00 0 
00638000-00717000 r-xp 00000000 08:01 3935829    /usr/lib/libstdc++.so.6.0.14
00717000-0071b000 r--p 000de000 08:01 3935829    /usr/lib/libstdc++.so.6.0.14
0071b000-0071c000 rw-p 000e2000 08:01 3935829    /usr/lib/libstdc++.so.6.0.14
0071c000-00723000 rw-p 00000000 00:00 0 
00909000-0092d000 r-xp 00000000 08:01 8781918    /lib/libm-2.12.1.so
0092d000-0092e000 r--p 00023000 08:01 8781918    /lib/libm-2.12.1.so
0092e000-0092f000 rw-p 00024000 08:01 8781918    /lib/libm-2.12.1.so
00fdb000-00ff5000 r-xp 00000000 08:01 8781903    /lib/libgcc_s.so.1
00ff5000-00ff6000 r--p 00019000 08:01 8781903    /lib/libgcc_s.so.1
00ff6000-00ff7000 rw-p 0001a000 08:01 8781903    /lib/libgcc_s.so.1
08048000-0804b000 r-xp 00000000 08:01 8652645    /home/akg/Desktop/contest/a.out
0804b000-0804c000 r--p 00002000 08:01 8652645    /home/akg/Desktop/contest/a.out
0804c000-0804d000 rw-p 00003000 08:01 8652645    /home/akg/Desktop/contest/a.out
09f93000-09fb4000 rw-p 00000000 00:00 0          [heap]
b7600000-b7621000 rw-p 00000000 00:00 0 
b7621000-b7700000 ---p 00000000 00:00 0 
b7765000-b7768000 rw-p 00000000 00:00 0 
b7775000-b7779000 rw-p 00000000 00:00 0 
bf9a7000-bf9c8000 rw-p 00000000 00:00 0          [stack]
Aborted

What does this mean? How can i get rid of it? I'm not using malloc or free , I'm just using vector!

Answer 1

Even if you're not allocating memory directly, it happens under the hood in vector code and you most likely corrupted some portion of memory by writing where you are not supposed to. The most likely reasons I can think of are:

1. Writing to an element that is out of bounds
2. Using a pointer/reference to an element that is no longer valid -- note that inserting more elements can invalidate earlier references

Of course, I can't say for sure unless you post some relevant code. Or try using valgrind to find the source of the problem.