Re: [libvirt] [PATCH 4/4] Add ATTRIBUTE_FALLTHROUGH for switch cases without break
On Wed, Feb 22, 2017 at 05:52:05PM +0000, Daniel P. Berrange wrote:
In GCC 7 there is a new warning triggered when a switch
case has a conditional statement (eg if ... else...) and
some of the code paths fallthrough to the next switch
statement. e.g.
conf/domain_conf.c: In function 'virDomainChrEquals':
conf/domain_conf.c:14926:12: error: this statement may fall through
[-Werror=implicit-fallthrough=]
if (src->targetTypeAttr != tgt->targetTypeAttr)
^
conf/domain_conf.c:14928:5: note: here
case VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE:
^~~~
conf/domain_conf.c: In function 'virDomainChrDefFormat':
conf/domain_conf.c:22143:12: error: this statement may fall through
[-Werror=implicit-fallthrough=]
if (def->targetTypeAttr) {
^
conf/domain_conf.c:22151:5: note: here
default:
^~~~~~~
GCC introduced a __attribute__((fallthrough)) to let you
indicate that this is intentionale behaviour rather than
a bug.
BTW, CLang has apparently had an -Wimplicit-fallthrough
warning flag for a while, and also seems to have the same
__attribute__((fallthrough)), but I've been unable to get
CLang to trigger such warnings, and hence did not enable
__attribute__((fallthrough)) on CLang. If someone can
figure out how to reproduce the warnings on clang we
could extend internal.h to surpress them for whichever
clang version introduced the warnings. As is, the
ATTRIBUTE_FALLTHROUGH turns into a no-op for CLang unless
it claims GCC 7.0 compatibility.
Regards,
Daniel
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