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make: Implicit Rules

 
 10 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 recipes 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
 compilation.
 
    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.
 

Menu

 
· Using Implicit              How to use an existing implicit rule
                                   to get the recipes for updating a file.
· Catalogue of Rules          A list of built-in 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 define a recipe for rules which
                                   cannot find any.
· Suffix Rules                The old-fashioned style of implicit rule.
· Implicit Rule Search        The precise algorithm for applying
                                   implicit rules.
 

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