GNU make manual 翻译(七十一)

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Secondary Expansion of Implicit Rules                        
-------------------------------------                        
                        
As `make' searches for an implicit rule, it substitutes the stem and then performs secondary expansion for every rule with a matching target pattern.  The value of the automatic variables is derived in the same fashion as for static pattern rules.  As an example:                           
     .SECONDEXPANSION:                     
                        
     foo: bar         
     foo foz: fo%: bo%  
     %oo: $$< $$^ $$+ $$*                        
                        
   When the implicit rule is tried for target `foo', `$$<' expands to `bar', `$$^' expands to `bar boo', `$$+' also expands to `bar boo', and `$$*' expands to `f'.                        

对隐式规则的二次扩展

当 make 搜寻一条 隐式规则，它替换枝干部分，并对每一条符合目的模式的规则进行二次扩展。

自动变量的值也像静态模式规则那样被推导处理。

例如：

.SECONDEXPANSION:

foo: bar

foo foz: fo%: bo%

%oo: $$< $$^ $$+ $$*

 

当隐式规则用于目的 foo时，$$< 扩展为 bar, $$^ 扩展为 bar boo， $$+也扩展为 bar boo，$$*扩展为 f。

后文待续