About once every three times I run my program, malloc reports a double error; eg.
myprogram(703,0xb06d9000) malloc: *** error for object 0x17dd0240: double free
*** set a breakpoint in malloc_error_break to debug
I have run the same code through valgrind more than a dozen times, but it never reports double free.
I ran the code through gdb with a breakpoint at malloc_error_break and (when an error occurs), the error is always reported in the standard C ++ library function. I isolated the parent function and injected it into the test unit, but there were no errors.
I think that the parent function / standard C ++ library is not to blame, it just frees what it allocates, and some other function in the parent program is freed.
I tried to see which object was freed twice, but my gdb skills were not able to find the first object that was freed. Please help me find which object caused the first free and, in addition, any help why my program generates this error. Thank.
Parent function comes down to:
int i;
double px, py;
int start, finish;
std::string comment;
std::vector<double> x, y;
std::fstream myfile;
myfile.open("filename.txt", std::ios_base::in);
std::getline(myfile, comment);
while(!myfile.eof())
{
myfile >> comment >> start >> comment >> finish;
for(i = 0; i <= finish-start; i++)
{
myfile >> px >> py;
x.push_back(px);
y.push_back(py);
}
}
EDIT: My data file looks something like this:
Comment: My Data
start 33 end 36
10.2 139.0076
9.22616 141.584
8.62802 141.083
8.87098 141.813
start 33 end 35
300.354 405
301.698 404.029
303.369 403.953
start 33 end 35
336.201 148.07
334.616 147.243
334.735 146.09
Backtrace from gdb
(gdb) backtrace
#0 0x93c2d4a9 in malloc_error_break ()
#1 0x93c28497 in szone_error ()
#2 0x93b52503 in szone_free ()
#3 0x93b5236d in free ()
#4 0x93b51f24 in localeconv_l ()
#5 0x93c18163 in strtod_l$UNIX2003 ()
#6 0x93c192e0 in strtod$UNIX2003 ()
#7 0x919b76e8 in std::__convert_to_v<double> ()
#8 0x919983cf in std::num_get<char, std::istreambuf_iterator<char, std::char_traits<char> > >::do_get ()
#9 0x91991671 in std::num_get<char, std::istreambuf_iterator<char, std::char_traits<char> > >::get ()
#10 0x9198d2dc in std::istream::operator>> ()
To repeat, I need help to find which object was first released, I'm not really interested in refactoring my code for this function, which I think is not causing a problem; if you don’t find something catastrophic in him.
EDIT: Changed example code.