• Kees Cook's avatar
    n_tty: Distribute switch variables for initialization · e24cd4e6
    Kees Cook authored
    Variables declared in a switch statement before any case statements
    cannot be automatically initialized with compiler instrumentation (as
    they are not part of any execution flow). With GCC's proposed automatic
    stack variable initialization feature, this triggers a warning (and they
    don't get initialized). Clang's automatic stack variable initialization
    (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also
    doesn't initialize such variables[1]. Note that these warnings (or silent
    skipping) happen before the dead-store elimination optimization phase,
    so even when the automatic initializations are later elided in favor of
    direct initializations, the warnings remain.
    
    To avoid these problems, move such variables into the "case" where
    they're used or lift them up into the main function body.
    
    drivers/tty/n_tty.c: In function ‘__process_echoes’:
    drivers/tty/n_tty.c:657:18: warning: statement will never be executed [-Wswitch-unreachable]
      657 |     unsigned int num_chars, num_bs;
          |                  ^~~~~~~~~
    
    [1] https://bugs.llvm.org/show_bug.cgi?id=44916Reviewed-by: default avatarJiri Slaby <jslaby@suse.cz>
    Signed-off-by: default avatarKees Cook <keescook@chromium.org>
    Link: https://lore.kernel.org/r/20200220062313.69209-1-keescook@chromium.orgSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    e24cd4e6
n_tty.c 61.6 KB