I typed "icov -f UTF-8 file" to the executable, the output was "illegal input sequence at position 24"

My binary compiled by g++, when I try to open it with gdbgui (written in python), it read it with utf-8, then shows me this error:

'utf-8' codec can't decode byte 0xf0 in position 24: invalid continuation byte

How can I fix this error manually, because I don't know how start to see the source for looking for the error with detail.

I typed icov -f UTF-8 file and the terminal said me that

ELF>iconv: illegal input sequence at position 24

That is not seen good in the text, but the output is this:

Output of file main:

$ file mainmain: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/l, for GNU/Linux 3.2.0, BuildID[sha1]=15d8a314b52498b7f0a6f16aec116e66d72fe589, not stripped

Output of file -i main:

$ file -i mainmain: application/x-sharedlib; charset=binary

The C++ source:

int main(){  int x,y;  x=13;  y=9;  if(x==y){    x=17;  } else{    x=23;  }  return 0;}