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Expand palloc/pg_malloc API for more type safety

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This adds additional variants of palloc, pg_malloc, etc. that
encapsulate common usage patterns and provide more type safety.

Specifically, this adds palloc_object(), palloc_array(), and
repalloc_array(), which take the type name of the object to be
allocated as its first argument and cast the return as a pointer to
that type.  There are also palloc0_object() and palloc0_array()
variants for initializing with zero, and pg_malloc_*() variants of all
of the above.

Inspired by the talloc library.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/bb755632-2a43-d523-36f8-a1e7a389a907@enterprisedb.com
This commit is contained in:
Peter Eisentraut 2022-09-12 08:31:56 +02:00
parent b060f57791
commit 2016055a92
2 changed files with 50 additions and 0 deletions
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28
src/include/common/fe_memutils.h
View File

@ -29,6 +29,28 @@ extern void *pg_malloc_extended(size_t size, int flags);
extern void *pg_realloc(void *pointer, size_t size);
extern void pg_free(void *pointer);
/*
* Variants with easier notation and more type safety
*/
/*
* Allocate space for one object of type "type"
*/
#define pg_malloc_object(type) ((type *) pg_malloc(sizeof(type)))
#define pg_malloc0_object(type) ((type *) pg_malloc0(sizeof(type)))
/*
* Allocate space for "count" objects of type "type"
*/
#define pg_malloc_array(type, count) ((type *) pg_malloc(sizeof(type) * (count)))
#define pg_malloc0_array(type, count) ((type *) pg_malloc0(sizeof(type) * (count)))
/*
* Change size of allocation pointed to by "pointer" to have space for "count"
* objects of type "type"
*/
#define pg_realloc_array(pointer, type, count) ((type *) pg_realloc(pointer, sizeof(type) * (count)))
/* Equivalent functions, deliberately named the same as backend functions */
extern char *pstrdup(const char *in);
extern char *pnstrdup(const char *in, Size size);
@ -38,6 +60,12 @@ extern void *palloc_extended(Size size, int flags);
extern void *repalloc(void *pointer, Size size);
extern void pfree(void *pointer);
#define palloc_object(type) ((type *) palloc(sizeof(type)))
#define palloc0_object(type) ((type *) palloc0(sizeof(type)))
#define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
#define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
#define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
/* sprintf into a palloc'd buffer --- these are in psprintf.c */
extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);
extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0);

22
src/include/utils/palloc.h
View File

@ -80,6 +80,28 @@ extern void *palloc_extended(Size size, int flags);
extern pg_nodiscard void *repalloc(void *pointer, Size size);
extern void pfree(void *pointer);
/*
* Variants with easier notation and more type safety
*/
/*
* Allocate space for one object of type "type"
*/
#define palloc_object(type) ((type *) palloc(sizeof(type)))
#define palloc0_object(type) ((type *) palloc0(sizeof(type)))
/*
* Allocate space for "count" objects of type "type"
*/
#define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
#define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
/*
* Change size of allocation pointed to by "pointer" to have space for "count"
* objects of type "type"
*/
#define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
/*
* The result of palloc() is always word-aligned, so we can skip testing
* alignment of the pointer when deciding which MemSet variant to use.