Re: a question of Chains of Implicit Rules

[Paul Smith]

On Wed, 2010-10-20 at 09:15 +0330, ali hagigat wrote:
> 10.4 Chains of Implicit Rules
> If the file ‘n.c’ exists, or is mentioned in the makefile, no special
> searching is required:
> make finds that the object file can be made by C compilation from ‘n.c’;
> later on, when
> considering how to make ‘n.c’, the rule for running Yacc is used.
> Ultimately both ‘n.c’
> and ‘n.o’ are updated.
> -----------------------------------------------------------------------------------------------------------------------
> "later on, when considering how to make ‘n.c’, the rule for running
> Yacc is used", what does it mean? Would you please give an example.

You have to read that paragraph in the context of the previous
paragraph, not all by itself:

> Sometimes a file can be made by a sequence of implicit rules.  For
> example, a file `N.o' could be made from `N.y' by running first Yacc
> and then `cc'.  Such a sequence is called a "chain".
> 
>    If the file `N.c' exists, or is mentioned in the makefile, no
> special searching is required: `make' finds that the object file can be
> made by C compilation from `N.c'; later on, when considering how to
> make `N.c', the rule for running Yacc is used.  Ultimately both `N.c'
> and `N.o' are updated.

Are you familiar with yacc and what it does?

Remember that make starts at the end (the final target to be built) and
walks backward; that's what the manual means by "later on".  If you read
the second paragraph with that in mind, and using the context in the
first paragraph, it might make more sense.

Or not.

-- 
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 Paul D. Smith <address@hidden>          Find some GNU make tips at:
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