Re: [libvirt] [PATCH 4/4] Add ATTRIBUTE_FALLTHROUGH for switch cases without break
On 02/22/2017 11:52 AM, 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)
^
+++ b/src/conf/domain_conf.c
@@ -14925,7 +14925,12 @@ virDomainChrEquals(virDomainChrDefPtr src,
case VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL:
if (src->targetTypeAttr != tgt->targetTypeAttr)
return false;
+
+ ATTRIBUTE_FALLTHROUGH;
+
I understand this one...
case VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE:
+ ATTRIBUTE_FALLTHROUGH;
+
case VIR_DOMAIN_CHR_DEVICE_TYPE_PARALLEL:
...but was this one necessary, or is gcc smart enough to know that two
consecutive labels never needs an explicit fallthrough?
Also, is it sufficient to spell it:
/* fall through */
so that Coverity can also recognize it? Or does gcc not recognize the
magic comment?
+++ b/src/internal.h
@@ -218,6 +218,10 @@
# endif
# endif
+# ifndef ATTRIBUTE_FALLTHROUGH
+# define ATTRIBUTE_FALLTHROUGH __attribute__((fallthrough))
+# endif
If the magic /* fall through */ comment is sufficient, then we don't
need this macro.
+++ b/src/lxc/lxc_container.c
@@ -2042,7 +2042,7 @@ static int lxcContainerDropCapabilities(virDomainDefPtr def,
default: /* User specified capabilities to drop */
toDrop = (state == VIR_TRISTATE_SWITCH_OFF);
}
- /* Fallthrough */
+ ATTRIBUTE_FALLTHROUGH;
Hmm - this argues at least one comment spelling that gcc does not recognize.
+++ b/tools/virsh-edit.c
@@ -140,7 +140,7 @@ do {
goto redefine;
break;
}
- /* fall-through */
+ ATTRIBUTE_FALLTHROUGH;
#endif
and another.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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