1 /*-------------------------------------------------------------------------
4 * POSTGRES memory allocator definitions.
6 * This file contains the basic memory allocation interface that is
7 * needed by almost every backend module. It is included directly by
8 * postgres.h, so the definitions here are automatically available
9 * everywhere. Keep it lean!
11 * Memory allocation occurs within "contexts". Every chunk obtained from
12 * palloc()/MemoryContextAlloc() is allocated within a specific context.
13 * The entire contents of a context can be freed easily and quickly by
14 * resetting or deleting the context --- this is both faster and less
15 * prone to memory-leakage bugs than releasing chunks individually.
16 * We organize contexts into context trees to allow fine-grain control
17 * over chunk lifetime while preserving the certainty that we will free
18 * everything that should be freed. See utils/mmgr/README for more info.
21 * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
22 * Portions Copyright (c) 1994, Regents of the University of California
24 * src/include/utils/palloc.h
26 *-------------------------------------------------------------------------
32 * Type MemoryContextData is declared in nodes/memnodes.h. Most users
33 * of memory allocation should just treat it as an abstract type, so we
34 * do not provide the struct contents here.
36 typedef struct MemoryContextData *MemoryContext;
39 * CurrentMemoryContext is the default allocation context for palloc().
40 * Avoid accessing it directly! Instead, use MemoryContextSwitchTo()
41 * to change the setting.
43 extern PGDLLIMPORT MemoryContext CurrentMemoryContext;
46 * Fundamental memory-allocation operations (more are in utils/memutils.h)
48 extern void *MemoryContextAlloc(MemoryContext context, Size size);
49 extern void *MemoryContextAllocZero(MemoryContext context, Size size);
50 extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
52 extern void *palloc(Size size);
53 extern void *palloc0(Size size);
54 extern void *repalloc(void *pointer, Size size);
55 extern void pfree(void *pointer);
58 * The result of palloc() is always word-aligned, so we can skip testing
59 * alignment of the pointer when deciding which MemSet variant to use.
60 * Note that this variant does not offer any advantage, and should not be
61 * used, unless its "sz" argument is a compile-time constant; therefore, the
62 * issue that it evaluates the argument multiple times isn't a problem in
65 #define palloc0fast(sz) \
66 ( MemSetTest(0, sz) ? \
67 MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
68 MemoryContextAllocZero(CurrentMemoryContext, sz) )
70 /* Higher-limit allocators. */
71 extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
72 extern void *repalloc_huge(void *pointer, Size size);
75 * MemoryContextSwitchTo can't be a macro in standard C compilers.
76 * But we can make it an inline function if the compiler supports it.
77 * See STATIC_IF_INLINE in c.h.
79 * Although this header file is nominally backend-only, certain frontend
80 * programs like pg_controldata include it via postgres.h. For some compilers
81 * it's necessary to hide the inline definition of MemoryContextSwitchTo in
82 * this scenario; hence the #ifndef FRONTEND.
87 extern MemoryContext MemoryContextSwitchTo(MemoryContext context);
88 #endif /* !PG_USE_INLINE */
89 #if defined(PG_USE_INLINE) || defined(MCXT_INCLUDE_DEFINITIONS)
90 STATIC_IF_INLINE MemoryContext
91 MemoryContextSwitchTo(MemoryContext context)
93 MemoryContext old = CurrentMemoryContext;
95 CurrentMemoryContext = context;
98 #endif /* PG_USE_INLINE || MCXT_INCLUDE_DEFINITIONS */
102 * These are like standard strdup() except the copied string is
103 * allocated in a context, not with malloc().
105 extern char *MemoryContextStrdup(MemoryContext context, const char *string);
106 extern char *pstrdup(const char *in);
107 extern char *pnstrdup(const char *in, Size len);
109 /* sprintf into a palloc'd buffer --- these are in psprintf.c */
111 psprintf(const char *fmt,...)
112 __attribute__((format(PG_PRINTF_ATTRIBUTE, 1, 2)));
114 pvsnprintf(char *buf, size_t len, const char *fmt, va_list args)
115 __attribute__((format(PG_PRINTF_ATTRIBUTE, 3, 0)));
117 #endif /* PALLOC_H */