《coredump问题原理探究》Linux x86版7.2节vector coredump例子
浏览数：118 /
时间：2015年06月20日
看一个coredump的例子:
[xuzhina@localhost s1_ex]$ gdb xuzhina_dump_c07_s1_ex core.27776 GNU gdb (GDB) Red Hat Enterprise Linux (7.2-75.el6) Copyright (C) 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "i686-redhat-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /home/xuzhina/code/s1_ex/xuzhina_dump_c07_s1_ex...(no debugging symbols found)...done. warning: core file may not match specified executable file. [New Thread 27776] Missing separate debuginfo for Try: yum --enablerepo='*-debug*' install /usr/lib/debug/.build-id/34/cbbfa23c72628894342b10c77f636b35126a7f Reading symbols from /usr/lib/libstdc++.so.6...(no debugging symbols found)...done. Loaded symbols for /usr/lib/libstdc++.so.6 Reading symbols from /lib/libm.so.6...(no debugging symbols found)...done. Loaded symbols for /lib/libm.so.6 Reading symbols from /lib/libgcc_s.so.1...(no debugging symbols found)...done. Loaded symbols for /lib/libgcc_s.so.1 Reading symbols from /lib/libc.so.6...(no debugging symbols found)...done. Loaded symbols for /lib/libc.so.6 Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done. Loaded symbols for /lib/ld-linux.so.2 Core was generated by `./xuzhina_dump_c07_s1_ex'. Program terminated with signal 11, Segmentation fault. #0 0x08048afb in __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > > std::merge<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > > >(__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >) () Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.149.el6_6.4.i686 libgcc-4.4.7-11.el6.i686 libstdc++-4.4.7-11.el6.i686 (gdb) bt #0 0x08048afb in __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > > std::merge<__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > > >(__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >, __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >) () #1 0x08048871 in main ()
看一下std::_Merge的汇编
(gdb) disassemble Dump of assembler code for function _ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_: 0x08048a88 <+0>: push %ebp 0x08048a89 <+1>: mov %esp,%ebp 0x08048a8b <+3>: push %esi 0x08048a8c <+4>: push %ebx 0x08048a8d <+5>: sub $0x20,%esp 0x08048a90 <+8>: mov 0x8(%ebp),%esi 0x08048a93 <+11>: jmp 0x8048b13 <_ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_+139> 0x08048a95 <+13>: lea 0x14(%ebp),%eax 0x08048a98 <+16>: mov %eax,(%esp) 0x08048a9b <+19>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048aa0 <+24>: mov (%eax),%ebx 0x08048aa2 <+26>: lea 0xc(%ebp),%eax 0x08048aa5 <+29>: mov %eax,(%esp) 0x08048aa8 <+32>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048aad <+37>: mov (%eax),%eax 0x08048aaf <+39>: cmp %eax,%ebx 0x08048ab1 <+41>: setl %al 0x08048ab4 <+44>: test %al,%al ---Type <return> to continue, or q <return> to quit--- 0x08048ab6 <+46>: je 0x8048ae1 <_ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_+89> 0x08048ab8 <+48>: lea 0x1c(%ebp),%eax 0x08048abb <+51>: mov %eax,(%esp) 0x08048abe <+54>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048ac3 <+59>: mov %eax,%ebx 0x08048ac5 <+61>: lea 0x14(%ebp),%eax 0x08048ac8 <+64>: mov %eax,(%esp) 0x08048acb <+67>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048ad0 <+72>: mov (%eax),%eax 0x08048ad2 <+74>: mov %eax,(%ebx) 0x08048ad4 <+76>: lea 0x14(%ebp),%eax 0x08048ad7 <+79>: mov %eax,(%esp) 0x08048ada <+82>: call 0x8048f5e <_ZN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEppEv> 0x08048adf <+87>: jmp 0x8048b08 <_ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_+128> 0x08048ae1 <+89>: lea 0x1c(%ebp),%eax 0x08048ae4 <+92>: mov %eax,(%esp) 0x08048ae7 <+95>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048aec <+100>: mov %eax,%ebx 0x08048aee <+102>: lea 0xc(%ebp),%eax 0x08048af1 <+105>: mov %eax,(%esp) 0x08048af4 <+108>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048af9 <+113>: mov (%eax),%eax => 0x08048afb <+115>: mov %eax,(%ebx) 0x08048afd <+117>: lea 0xc(%ebp),%eax 0x08048b00 <+120>: mov %eax,(%esp) 0x08048b03 <+123>: call 0x8048f5e <_ZN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEppEv> 0x08048b08 <+128>: lea 0x1c(%ebp),%eax 0x08048b0b <+131>: mov %eax,(%esp) 0x08048b0e <+134>: call 0x8048f5e <_ZN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEppEv> 0x08048b13 <+139>: lea 0x10(%ebp),%eax 0x08048b16 <+142>: mov %eax,0x4(%esp) 0x08048b1a <+146>: lea 0xc(%ebp),%eax 0x08048b1d <+149>: mov %eax,(%esp) 0x08048b20 <+152>: call 0x8048f27 <_ZN9__gnu_cxxneIPiSt6vectorIiSaIiEEEEbRKNS_17__normal_iteratorIT_T0_EESA_> 0x08048b25 <+157>: test %al,%al 0x08048b27 <+159>: je 0x8048b46 <_ZSt5mergeIN9__gnu_cxx17__normal_itera
由上面汇编可以看出,崩溃指令的ebx刚好是
__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >::operator*() const
的返回值,而这个成员函数的this指针由
0x08048ae1 <+89>: lea 0x1c(%ebp),%eax 0x08048ae4 <+92>: mov %eax,(%esp) 0x08048ae7 <+95>: call 0x8048f54 <_ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv> 0x08048aec <+100>: mov %eax,%ebx
是从第六个参数(ebp+0x1c)获取的.
而这个函数的实现:
(gdb) disassemble 0x8048f54 Dump of assembler code for function _ZNK9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEdeEv: 0x08048f54 <+0>: push %ebp 0x08048f55 <+1>: mov %esp,%ebp 0x08048f57 <+3>: mov 0x8(%ebp),%eax 0x08048f5a <+6>: mov (%eax),%eax 0x08048f5c <+8>: pop %ebp 0x08048f5d <+9>: ret End of assembler dump.
可见,这个函数仅仅是把this指针指向的第一个成员的值返回了.
那么,只能看上一层的函数main函数来确定一下这个this指针究竟是怎么回事吧.
(gdb) frame 1 #1 0x08048871 in main () (gdb) disassemble Dump of assembler code for function main: 0x08048774 <+0>: lea 0x4(%esp),%ecx 0x08048778 <+4>: and $0xfffffff0,%esp 0x0804877b <+7>: pushl -0x4(%ecx) 0x0804877e <+10>: push %ebp 0x0804877f <+11>: mov %esp,%ebp 0x08048781 <+13>: push %esi 0x08048782 <+14>: push %ebx 0x08048783 <+15>: push %ecx 0x08048784 <+16>: sub $0x7c,%esp 0x08048787 <+19>: lea -0x44(%ebp),%eax 0x0804878a <+22>: mov %eax,(%esp) 0x0804878d <+25>: call 0x8048958 <_ZNSt6vectorIiSaIiEEC2Ev> 0x08048792 <+30>: movl $0x1,-0x38(%ebp) 0x08048799 <+37>: lea -0x38(%ebp),%eax 0x0804879c <+40>: mov %eax,0x4(%esp) 0x080487a0 <+44>: lea -0x44(%ebp),%eax 0x080487a3 <+47>: mov %eax,(%esp) 0x080487a6 <+50>: call 0x80489ca <_ZNSt6vectorIiSaIiEE9push_backERKi> 0x080487ab <+55>: lea -0x50(%ebp),%eax 0x080487ae <+58>: mov %eax,(%esp) 0x080487b1 <+61>: call 0x8048958 <_ZNSt6vectorIiSaIiEEC2Ev> 0x080487b6 <+66>: movl $0x8,-0x34(%ebp) ---Type <return> to continue, or q <return> to quit--- 0x080487bd <+73>: lea -0x34(%ebp),%eax 0x080487c0 <+76>: mov %eax,0x4(%esp) 0x080487c4 <+80>: lea -0x50(%ebp),%eax 0x080487c7 <+83>: mov %eax,(%esp) 0x080487ca <+86>: call 0x80489ca <_ZNSt6vectorIiSaIiEE9push_backERKi> 0x080487cf <+91>: lea -0x5c(%ebp),%eax 0x080487d2 <+94>: mov %eax,(%esp) 0x080487d5 <+97>: call 0x8048958 <_ZNSt6vectorIiSaIiEEC2Ev> 0x080487da <+102>: lea -0x2c(%ebp),%eax 0x080487dd <+105>: lea -0x5c(%ebp),%edx 0x080487e0 <+108>: mov %edx,0x4(%esp) 0x080487e4 <+112>: mov %eax,(%esp) 0x080487e7 <+115>: call 0x8048a3e <_ZNSt6vectorIiSaIiEE5beginEv> 0x080487ec <+120>: sub $0x4,%esp 0x080487ef <+123>: lea -0x28(%ebp),%eax 0x080487f2 <+126>: lea -0x50(%ebp),%edx 0x080487f5 <+129>: mov %edx,0x4(%esp) 0x080487f9 <+133>: mov %eax,(%esp) 0x080487fc <+136>: call 0x8048a62 <_ZNSt6vectorIiSaIiEE3endEv> 0x08048801 <+141>: sub $0x4,%esp 0x08048804 <+144>: lea -0x24(%ebp),%eax 0x08048807 <+147>: lea -0x50(%ebp),%edx 0x0804880a <+150>: mov %edx,0x4(%esp) ---Type <return> to continue, or q <return> to quit--- 0x0804880e <+154>: mov %eax,(%esp) 0x08048811 <+157>: call 0x8048a3e <_ZNSt6vectorIiSaIiEE5beginEv> 0x08048816 <+162>: sub $0x4,%esp 0x08048819 <+165>: lea -0x20(%ebp),%eax 0x0804881c <+168>: lea -0x44(%ebp),%edx 0x0804881f <+171>: mov %edx,0x4(%esp) 0x08048823 <+175>: mov %eax,(%esp) 0x08048826 <+178>: call 0x8048a62 <_ZNSt6vectorIiSaIiEE3endEv> 0x0804882b <+183>: sub $0x4,%esp 0x0804882e <+186>: lea -0x1c(%ebp),%eax 0x08048831 <+189>: lea -0x44(%ebp),%edx 0x08048834 <+192>: mov %edx,0x4(%esp) 0x08048838 <+196>: mov %eax,(%esp) 0x0804883b <+199>: call 0x8048a3e <_ZNSt6vectorIiSaIiEE5beginEv> 0x08048840 <+204>: sub $0x4,%esp 0x08048843 <+207>: lea -0x30(%ebp),%eax 0x08048846 <+210>: mov -0x2c(%ebp),%edx 0x08048849 <+213>: mov %edx,0x14(%esp) 0x0804884d <+217>: mov -0x28(%ebp),%edx 0x08048850 <+220>: mov %edx,0x10(%esp) 0x08048854 <+224>: mov -0x24(%ebp),%edx 0x08048857 <+227>: mov %edx,0xc(%esp) 0x0804885b <+231>: mov -0x20(%ebp),%edx ---Type <return> to continue, or q <return> to quit--- 0x0804885e <+234>: mov %edx,0x8(%esp) 0x08048862 <+238>: mov -0x1c(%ebp),%edx 0x08048865 <+241>: mov %edx,0x4(%esp) 0x08048869 <+245>: mov %eax,(%esp) 0x0804886c <+248>: call 0x8048a88 <_ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_> => 0x08048871 <+253>: sub $0x4,%esp 0x08048874 <+256>: mov $0x0,%ebx 0x08048879 <+261>: lea -0x5c(%ebp),%eax 0x0804887c <+264>: mov %eax,(%esp) 0x0804887f <+267>: call 0x804896c <_ZNSt6vectorIiSaIiEED2Ev> 0x08048884 <+272>: jmp 0x80488b0 <main+316> 0x08048886 <+274>: mov %edx,%ebx 0x08048888 <+276>: mov %eax,%esi 0x0804888a <+278>: lea -0x5c(%ebp),%eax 0x0804888d <+281>: mov %eax,(%esp) 0x08048890 <+284>: call 0x804896c <_ZNSt6vectorIiSaIiEED2Ev> 0x08048895 <+289>: mov %esi,%eax 0x08048897 <+291>: mov %ebx,%edx 0x08048899 <+293>: jmp 0x804889b <main+295> 0x0804889b <+295>: mov %edx,%ebx 0x0804889d <+297>: mov %eax,%esi 0x0804889f <+299>: lea -0x50(%ebp),%eax ---Type <return> to continue, or q <return> to quit---
由
0x08048846 <+210>: mov -0x2c(%ebp),%edx 0x08048849 <+213>: mov %edx,0x14(%esp) 0x0804884d <+217>: mov -0x28(%ebp),%edx 0x08048850 <+220>: mov %edx,0x10(%esp) 0x08048854 <+224>: mov -0x24(%ebp),%edx 0x08048857 <+227>: mov %edx,0xc(%esp) 0x0804885b <+231>: mov -0x20(%ebp),%edx ---Type <return> to continue, or q <return> to quit--- 0x0804885e <+234>: mov %edx,0x8(%esp) 0x08048862 <+238>: mov -0x1c(%ebp),%edx 0x08048865 <+241>: mov %edx,0x4(%esp) 0x08048869 <+245>: mov %eax,(%esp) 0x0804886c <+248>: call 0x8048a88 <_ZSt5mergeIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEES6_S6_ET1_T_S8_T0_S9_S7_> => 0x08048871 <+253>: sub $0x4,%esp
可以看到第六个参数，应该是由ebp-0x2c的值.
而ebp-0x2c如何得来？看一下这段汇编：
0x080487cf <+91>: lea -0x5c(%ebp),%eax 0x080487d2 <+94>: mov %eax,(%esp) 0x080487d5 <+97>: call 0x8048958 <_ZNSt6vectorIiSaIiEEC2Ev> 0x080487da <+102>: lea -0x2c(%ebp),%eax 0x080487dd <+105>: lea -0x5c(%ebp),%edx 0x080487e0 <+108>: mov %edx,0x4(%esp) 0x080487e4 <+112>: mov %eax,(%esp) 0x080487e7 <+115>: call 0x8048a3e <_ZNSt6vectorIiSaIiEE5beginEv>
用c++filt命令可以看到. _ZNSt6vectorIiSaIiEEC2Ev和_ZNSt6vectorIiSaIiEE5beginEv是
[xuzhina@localhost s1_ex]$ c++filt _ZNSt6vectorIiSaIiEEC2Ev std::vector<int, std::allocator<int> >::vector() [xuzhina@localhost s1_ex]$ c++filt _ZNSt6vectorIiSaIiEE5beginEv std::vector<int, std::allocator<int> >::begin()
可知ebp-0x2c的值是由ebp-0x5c得来的。
看一下ebp-0x5c里存放着的是什么.
(gdb) x /4x $ebp-0x5c 0xbfb2b24c: 0x00000000 0x00000000 0x00000000 0x0865e018
可以看到ebp-0x54指向的vector对象, _M_start, _M_finish, _M_end_of_storage
三个指针都为0.说明vector只是调用完了构造函数,却没有进行别的操作来申请空间.
看一下源代码
1 #include <vector>
2 #include <algorithm>
3 #include <iostream>
4
5 int main()
6 {
7 std::vector<int> a;
8 a.push_back(1);
9
10 std::vector<int> b;
11 b.push_back(8);
12
13 std::vector<int> c;
14 std::merge( a.begin(), a.end(), b.begin(), b.end(), c.begin() );
15
16 return 0;
17 }
可知,只有c这个vector对象只是构造了,没有申请任何空间,就进行了merge操作.在merge之前,可以调用一下成员函数reserve.
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