Basic Memory Management
The most basic usage of pools is for memory management. Instead of
mytype* myvar = malloc(sizeof(mytype)) ;
/* make sure it gets freed later in every possible execution path */
we use
mytype* myvar = apr_palloc(pool, sizeof(mytype)) ;
and the pool automatically takes responsibility for freeing it, regardless
of what may happen in the meantime.
This takes many forms in APR and Apache, where memory is allocated within
another function. Examples are string manipulation functions and logging,
where we gain the immediate benefit of being able to use constructs like
the APR version of sprintf() without having to know the size of a string
in advance:
char* result = apr_psprintf(pool, fmt, ...) ;
APR also provides higher-level abstractions of pool memory, for example
in the buckets used to pass data down the filter chain. But we'll keep
those for another article.
