Function getdelim 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn getdelim(
    lineptr: *mut *mut c_char,
    n: *mut size_t,
    delim: c_int,
    stream: *mut FILE,
) -> ssize_t

https://pubs.opengroup.org/onlinepubs/9799919799/functions/getline.html

Safety

• lineptr, *lineptr, n, stream` pointers must be valid and have to be aligned.
• stream has to be a valid file handle returned by fopen and likes.

Deviation from POSIX

• EINVAL is set on stream being NULL or delim not fitting into char (POSIX allows UB)
• *n can contain invalid data. The buffer size n is not read, instead realloc is called each time. That is in principle inefficent since the buffer is reallocated in memory for every call, but if n is by mistake bigger than the number of bytes allocated for the buffer, there can be no out-of-bounds write.
• On non-stream-related errors, the error indicator of the stream is not set. Posix states “If an error occurs, the error indicator for the stream shall be set, and the function shall return -1 and set errno to indicate the error.” but in cases that produce EINVAL even glibc doesn’t seem to set the error indicator, so we also don’t.