Roland Ver. 4.5 Informações Técnicas descarregar pdf (Página 149)

Chapter 12: Extending GNU make 139

gmk_expand

This function takes a string and expands it using make expansion rules. The

result of the expansion is returned in a nil-terminated string buﬀer. The caller

is responsible for calling gmk_free with a pointer to the returned buﬀer when

done.

gmk_eval This function takes a buﬀer and evaluates it as a segment of makeﬁle syntax.

This function can be used to deﬁne new variables, new rules, etc. It is equivalent

to using the eval make function.

Note that there is a diﬀerence between gmk_eval and calling gmk_expand with a string

using the eval function: in the latter case the string will be expanded twice; once by gmk_

expand and then again by the eval function. Using gmk_eval the buﬀer is only expanded

once, at most (as it’s read by the make parser).

Memory Management

Some systems allow for diﬀerent memory management schemes. Thus you should never

pass memory that you’ve allocated directly to any make function, nor should you attempt

to directly free any memory returned to you by any make function. Instead, use the gmk_

alloc and gmk_free functions.

In particular, the string returned to make by a function registered using gmk_add_

function must be allocated using gmk_alloc, and the string returned from the make gmk_

expand function must be freed (when no longer needed) using gmk_free.

gmk_alloc

Return a pointer to a newly-allocated buﬀer. This function will always return

a valid pointer; if not enough memory is available make will exit.

gmk_free Free a buﬀer returned to you by make. Once the gmk_free function returns the

string will no longer be valid.

12.2.4 Example Loaded Object

Let’s suppose we wanted to write a new GNU make function that would create a temporary

ﬁle and return its name. We would like our function to take a preﬁx as an argument. First

we can write the function in a ﬁle mk_temp.c:

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Roland Ver. 4.5 Informações Técnicas Página 149