Re: [libvirt] [PATCHv2] build: correctly check for SOICGIFVLAN GET_VLAN_VID_CMD command

> > AC_CHECK_DECLS unconditionally defines the variable to either 0 or 1, so > checking if it is defined will still fail to compile on older headers > that lack the enum; Well, it would have compiled successfully, but compiled the wrong code :-) > what you want is to check that it has a non-zero value. Now that I've seen this, it bugs me that all HAVE_* #defines aren't consistent about this - some are undefined if the capability is missing, and some are #defined, but to 0.