关于poky中.conf文件=， ?=, ??=的区别

[09:10] == bigwatercar [dd0b0722@gateway/web/freenode/ip.221.11.7.34] has joined #poky[09:10] <bigwatercar> What's the meaning of "??=" in .conf file?[09:12] <bigwatercar> What's the meaning of "??=" in .conf file?[09:13] <Daemon404> iirc, it means "set it if it isn't set already", and = and ?= get precedence over it.[09:13] <Daemon404> i think.[09:15] <bigwatercar> you think? Are you sure?[09:16] <Daemon404> there was a mail on poky-devel recently that explaiend this[09:16] <Daemon404> im trying to find it for you[09:16] <bigwatercar> Thank you very much.[09:17] <Daemon404> thunderbird does not liek searching for "?=|[09:17] <Daemon404> grep time...[09:19] <bigwatercar> There is little chinese documents, so poky is difficult for me.[09:19] <Daemon404> several chinese folks work on it, so it's possible they may show up At Some Point (TM)[09:20] <bigwatercar> ahh[09:24] <Daemon404> http://pokylinux.org/doc/poky-handbook.html#structure-build-conf-local.conf[09:24] <Daemon404> there[09:24] <Daemon404> and ??= gets lower precedence than ?=[09:25] <bigwatercar> It describes the difference between = and ?=[09:26] <Daemon404> ??= acts like ?=, except that ?= has higher precedence[09:26] <bigwatercar> Now I understand it.[09:26] <bigwatercar> Thank you Daemon404[09:27] <Daemon404> no problem[09:27] <bigwatercar> :D