Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH] n_tty: Distribute switch variables for initialization | Date | Wed, 19 Feb 2020 22:23:13 -0800 |
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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=44916
Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index f9c584244f72..1d1a398f4981 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -654,9 +654,9 @@ static size_t __process_echoes(struct tty_struct *tty) op = echo_buf(ldata, tail + 1); switch (op) { + case ECHO_OP_ERASE_TAB: { unsigned int num_chars, num_bs; - case ECHO_OP_ERASE_TAB: if (MASK(ldata->echo_commit) == MASK(tail + 2)) goto not_yet_stored; num_chars = echo_buf(ldata, tail + 2); @@ -687,7 +687,7 @@ static size_t __process_echoes(struct tty_struct *tty) } tail += 3; break; - + } case ECHO_OP_SET_CANON_COL: ldata->canon_column = ldata->column; tail += 2;
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