stderr (GNU Gnulib)

Gnulib module: —

Portability problems fixed by Gnulib:

Portability problems not fixed by Gnulib:

stderr is created in 32-bit mode instead of 64-bit mode: Cygwin 1.5.x. One workaround is to use freopen(NULL, "r+", stderr) on Cygwin 1.5.21 or newer. Another is to use the gnulib ftello module and do ftello(stderr).
POSIX states that a setuid application can guarantee that fd 2 is open, but some systems guarantee this even for non-setuid programs. If an application is executed with fd 2 closed, use of stderr can affect an unrelated file that happened to be assigned to fd 2. The gnulib xstdopen or the *-safer modules may be used to guarantee that fd 2 stays reserved for stderr.