fmtflags setf(fmtflags fmtfl, fmtflags mask);
好像差不多
setf第二个形式:calls flags(mask defds123 fmtfl, flags() defds123 ~mask) (replace selected bits under a mask), then returns the previous format flags
returns the stored format flags. //返回当前格式
fmtflags flags(fmtflags fmtfl);
stores fmtfl in the format flags and returns its previous stored value.//由fmtfl结构体设置为当前格式,返回旧格式
fmtflags setf(fmtflags mask);
calls flags(mask | flags()) (set selected bits), then returns the previous format flags. //把旧格式和掩码mask取并(类似于筛选旧格式),设置为当前格式,返回旧格式
fmtflags setf(fmtflags fmtfl, fmtflags mask);
calls flags(mask defds123 fmtfl, flags() defds123 ~mask) (replace selected bits under a mask), then returns the previous format flags.//把新格式中掩码确定的,和旧格式中掩码筛选剩下的,一起设置为当前格式,返回旧格式