writev() with bad address and zero size

[kimjs29]

writev() uses struct iovec which has iov_base and iov_len members.

In Linux writev() permits bad address in iov_base in case of zero iov_len value.
In WSL writev() generates an error in this case.
iov_len must be checked against zero before iov_base should be valid.

I found this case in debugging of CMake's configure_file which calls eventually ofstream::write(buf,siz) where siz is 1024 or more.

#include <sys/uio.h> // for writev & struct iov
#include <stdio.h>   // for perror
int main()
{
    struct iovec iov = {0,0};
    if (writev(2, &iov, 1) < 0)
        perror("writev() error: ");
}

[benhillis]

Thanks for reporting this, this was also reported in #238 and #272. I'm going to go ahead and close this out because it's being tracked by the other two issues.

Thanks again!