(make.info)Implicit Rules

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Using Implicit Rules

   Certain standard ways of remaking target files are used very often.
For example, one customary way to make an object file is from a C
source file using the C compiler, `cc'.

   "Implicit rules" tell `make' how to use customary techniques so that
you do not have to specify them in detail when you want to use them.
For example, there is an implicit rule for C compilation.  File names
determine which implicit rules are run.  For example, C compilation
typically takes a `.c' file and makes a `.o' file.  So `make' applies
the implicit rule for C compilation when it sees this combination of
file name endings.

   A chain of implicit rules can apply in sequence; for example, `make'
will remake a `.o' file from a `.y' file by way of a `.c' file.

   The built-in implicit rules use several variables in their commands
so that, by changing the values of the variables, you can change the
way the implicit rule works.  For example, the variable `CFLAGS'
controls the flags given to the C compiler by the implicit rule for C

   You can define your own implicit rules by writing "pattern rules".

   "Suffix rules" are a more limited way to define implicit rules.
Pattern rules are more general and clearer, but suffix rules are
retained for compatibility.

* Using Implicit
How to use an existing implicit rule to get the commands for updating a file.
* Catalogue of Rules
A list of built-in implicit rules.
* Implicit Variables
How to change what predefined rules do.
* Chained Rules
How to use a chain of implicit rules.
* Pattern Rules
How to define new implicit rules.
* Last Resort
How to defining commands for rules which cannot find any.
* Suffix Rules
The old-fashioned style of implicit rule.
* Search Algorithm
The precise algorithm for applying implicit rules.

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