lib: Fix unchecked return value

[ShubhamDesai]

This pull request address "unchecked return value from library". The issue is identified by coverity scan (CID : 1207295, 1207291,1207292,1207294, 1207293).

All instances of remove(filename) are replaced with

if (remove(filename) != 0) {
            G_fatal_error(_("Unable to remove file %s"), filename);
}

[ShubhamDesai]

not sure whether to use G_warning or G_fatal_error

[wenzeslaus]

Warning versus error is not clear to me either. RTreeNewIndex gets file descriptor from an open call on a temporary file name, but then the file is deleted. I understand this is cleanup, but the behavior is not clear to me and so I can't decide on whether ignoring, warning, or erroring is the right thing to do.

[ShubhamDesai]

Warning versus error is not clear to me either. RTreeNewIndex gets file descriptor from an open call on a temporary file name, but then the file is deleted. I understand this is cleanup, but the behavior is not clear to me and so I can't decide on whether ignoring, warning, or erroring is the right thing to do.

Initially i used G_fatal_error so with that all test cases passed on Mac and ubuntu but failed on Windows.
when i checked the testcases most of them displayed error message with Unable to remove file.
i think because in windows systems a file cannot be removed without closing it. So added another check where first file descriptor is closed and then an attempt is made to remove the file.

Anyways for now with G_fatal i could identify the issue for closing the file descriptor and then attempt to remove

[wenzeslaus]

i think because in windows systems a file cannot be removed without closing it.

Great catch. Closing seems indeed appropriate.