On Fri, Mar 6, 2020 at 9:36 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > On Fri, Mar 6, 2020 at 9:32 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > 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 > > That's not good, have you filed a bug against Clang yet? It should at > least warn when the corresponding stack init flag is set. D'oh, link is below. > > > 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, lift such variables up into the next code > > block. > > > > drivers/gpu/drm/drm_edid.c: In function ‘drm_edid_to_eld’: > > drivers/gpu/drm/drm_edid.c:4395:9: warning: statement will never be > > executed [-Wswitch-unreachable] > > 4395 | int sad_count; > > | ^~~~~~~~~ > > > > [1] https://bugs.llvm.org/show_bug.cgi?id=44916 > > > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > > --- > > v2: move into function block instead being switch-local (Ville Syrjälä) > > --- > > drivers/gpu/drm/drm_edid.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > > index 805fb004c8eb..46cee78bc175 100644 > > --- a/drivers/gpu/drm/drm_edid.c > > +++ b/drivers/gpu/drm/drm_edid.c > > @@ -4381,6 +4381,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) > > > > if (cea_revision(cea) >= 3) { > > int i, start, end; > > + int sad_count; > > > > if (cea_db_offsets(cea, &start, &end)) { > > start = 0; > > @@ -4392,8 +4393,6 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) > > dbl = cea_db_payload_len(db); > > > > switch (cea_db_tag(db)) { > > - int sad_count; > > - > > case AUDIO_BLOCK: > > /* Audio Data Block, contains SADs */ > > sad_count = min(dbl / 3, 15 - total_sad_count); > > -- > > 2.20.1 > > > > > > -- > > Kees Cook > > > > -- > > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202003060930.DDCCB6659%40keescook. > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
