问题
The part of the code which gives rise to the segmentation fault is given below.
ifstream xiFileId(xifile, ios::binary); //xifile is a char *
//the ii_t class in the following line is taken from http://stackoverflow.com/questions/1855704/c-binary-file-i-o-to-from-containers-other-than-char-using-stl-algorithms written by http://stackoverflow.com/users/14065/loki-astari
ii_t<uint> xi_in(xiFileId);
copy(xi_in, ii_t<uint>(), xi.data()); //xi is a 2D boost::multi_array
//my efforts to debug
ios::iostate s = xiFileId.rdstate();
if(s & ios::badbit) cout << "bad bit is set" << endl;
if (s & ios::failbit) cout << "fail bit is set" << endl;
if (s & ios::eofbit) cout << "eof bit is set" << endl;
if (s & ios::goodbit) cout << "good bit is set" << endl;
xiFileId.close(); //this line creates the seg violation
It is found that the failbit and eof bit are set. Using valgrind it was found that there is no memory leak for my whole program.
The same code (as above) is repeated for another binary file and a segmentation fault does not arise when closing that file (that file is closed earlier) even though that file also has both fail and eof bit set.
That file closing give rise to segmentation fault is identified by using gdb and the core file, which is given below.
#0 0x00007f16ad99ae50 in __libc_free (mem=0x1b8f930) at malloc.c:3724
3724 malloc.c: No such file or directory.
in malloc.c
(gdb) bt
#0 0x00007f16ad99ae50 in __libc_free (mem=0x1b8f930) at malloc.c:3724
#1 0x00007f16ae1adf0e in std::basic_filebuf<char, std::char_traits<char> >::_M_destroy_internal_buffer() () from /usr/lib/libstdc++.so.6
#2 0x00007f16ae1af4d4 in std::basic_filebuf<char, std::char_traits<char> >::close() () from /usr/lib/libstdc++.so.6
#3 0x00007f16ae1b133d in std::basic_ifstream<char, std::char_traits<char> >::close() () from /usr/lib/libstdc++.so.6
#4 0x000000000040c119 in main (argc=19, argv=0x7fff05849898) at prediction.cpp:161
If I remove the xiFileId.close(); as the compiler will close the file when it becomes out of scope, the gdb back trace gives the following:
#0 0x00007f97fab81e50 in __libc_free (mem=0x15a7930) at malloc.c:3724
3724 malloc.c: No such file or directory.
in malloc.c
(gdb) bt
#0 0x00007f97fab81e50 in __libc_free (mem=0x15a7930) at malloc.c:3724
#1 0x00007f97fb394f0e in std::basic_filebuf<char, std::char_traits<char> >::_M_destroy_internal_buffer() () from /usr/lib/libstdc++.so.6
#2 0x00007f97fb3964d4 in std::basic_filebuf<char, std::char_traits<char> >::close() () from /usr/lib/libstdc++.so.6
#3 0x00007f97fb39c966 in std::basic_ifstream<char, std::char_traits<char> >::~basic_ifstream() () from /usr/lib/libstdc++.so.6
#4 0x000000000040c184 in main (argc=19, argv=0x7fff59b71918) at prediction.cpp:163
which shows that the ~basic_ifstream() is called and segmentation violation occurs.
Under what conditions a file closing can create a seg violation?
Any ideas on how can I investigate further/fix it?
This code is run on Ubuntu 10.04 and compiled using gcc version 4.4.3 .
suresh
回答1:
The solution is already mentioned in the comments but for the convenience of future readers, it is posted as an answer seperately.
The problem was with the ii_t class and a solution was provided in Segmentation fault on boost::multi_array
by https://stackoverflow.com/users/12711/michael-burr
来源：https://stackoverflow.com/questions/8003532/segmentation-fault-on-closing-a-binary-file