Age Owner TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * palloc.h
4 : * POSTGRES memory allocator definitions.
5 : *
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!
10 : *
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.
19 : *
20 : *
21 : * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
22 : * Portions Copyright (c) 1994, Regents of the University of California
23 : *
24 : * src/include/utils/palloc.h
25 : *
26 : *-------------------------------------------------------------------------
27 : */
28 : #ifndef PALLOC_H
29 : #define PALLOC_H
30 :
31 : /*
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.
35 : */
36 : typedef struct MemoryContextData *MemoryContext;
37 :
38 : /*
39 : * A memory context can have callback functions registered on it. Any such
40 : * function will be called once just before the context is next reset or
41 : * deleted. The MemoryContextCallback struct describing such a callback
42 : * typically would be allocated within the context itself, thereby avoiding
43 : * any need to manage it explicitly (the reset/delete action will free it).
44 : */
45 : typedef void (*MemoryContextCallbackFunction) (void *arg);
46 :
47 : typedef struct MemoryContextCallback
48 : {
49 : MemoryContextCallbackFunction func; /* function to call */
50 : void *arg; /* argument to pass it */
51 : struct MemoryContextCallback *next; /* next in list of callbacks */
52 : } MemoryContextCallback;
53 :
54 : /*
55 : * CurrentMemoryContext is the default allocation context for palloc().
56 : * Avoid accessing it directly! Instead, use MemoryContextSwitchTo()
57 : * to change the setting.
58 : */
59 : extern PGDLLIMPORT MemoryContext CurrentMemoryContext;
60 :
61 : /*
62 : * Flags for MemoryContextAllocExtended.
63 : */
64 : #define MCXT_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
65 : #define MCXT_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
66 : #define MCXT_ALLOC_ZERO 0x04 /* zero allocated memory */
67 :
68 : /*
69 : * Fundamental memory-allocation operations (more are in utils/memutils.h)
70 : */
71 : extern void *MemoryContextAlloc(MemoryContext context, Size size);
72 : extern void *MemoryContextAllocZero(MemoryContext context, Size size);
73 : extern void *MemoryContextAllocZeroAligned(MemoryContext context, Size size);
74 : extern void *MemoryContextAllocExtended(MemoryContext context,
75 : Size size, int flags);
76 : extern void *MemoryContextAllocAligned(MemoryContext context,
77 : Size size, Size alignto, int flags);
78 :
79 : extern void *palloc(Size size);
80 : extern void *palloc0(Size size);
81 : extern void *palloc_extended(Size size, int flags);
82 : extern void *palloc_aligned(Size size, Size alignto, int flags);
83 : extern pg_nodiscard void *repalloc(void *pointer, Size size);
84 : extern pg_nodiscard void *repalloc_extended(void *pointer,
85 : Size size, int flags);
86 : extern pg_nodiscard void *repalloc0(void *pointer, Size oldsize, Size size);
87 : extern void pfree(void *pointer);
88 :
89 : /*
90 : * Variants with easier notation and more type safety
91 : */
92 :
93 : /*
94 : * Allocate space for one object of type "type"
95 : */
96 : #define palloc_object(type) ((type *) palloc(sizeof(type)))
97 : #define palloc0_object(type) ((type *) palloc0(sizeof(type)))
98 :
99 : /*
100 : * Allocate space for "count" objects of type "type"
101 : */
102 : #define palloc_array(type, count) ((type *) palloc(sizeof(type) * (count)))
103 : #define palloc0_array(type, count) ((type *) palloc0(sizeof(type) * (count)))
104 :
105 : /*
106 : * Change size of allocation pointed to by "pointer" to have space for "count"
107 : * objects of type "type"
108 : */
109 : #define repalloc_array(pointer, type, count) ((type *) repalloc(pointer, sizeof(type) * (count)))
110 : #define repalloc0_array(pointer, type, oldcount, count) ((type *) repalloc0(pointer, sizeof(type) * (oldcount), sizeof(type) * (count)))
111 :
112 : /*
113 : * The result of palloc() is always word-aligned, so we can skip testing
114 : * alignment of the pointer when deciding which MemSet variant to use.
115 : * Note that this variant does not offer any advantage, and should not be
116 : * used, unless its "sz" argument is a compile-time constant; therefore, the
117 : * issue that it evaluates the argument multiple times isn't a problem in
118 : * practice.
119 : */
120 : #define palloc0fast(sz) \
121 : ( MemSetTest(0, sz) ? \
122 : MemoryContextAllocZeroAligned(CurrentMemoryContext, sz) : \
123 : MemoryContextAllocZero(CurrentMemoryContext, sz) )
124 :
125 : /* Higher-limit allocators. */
126 : extern void *MemoryContextAllocHuge(MemoryContext context, Size size);
127 : extern pg_nodiscard void *repalloc_huge(void *pointer, Size size);
128 :
129 : /*
130 : * Although this header file is nominally backend-only, certain frontend
131 : * programs like pg_controldata include it via postgres.h. For some compilers
132 : * it's necessary to hide the inline definition of MemoryContextSwitchTo in
133 : * this scenario; hence the #ifndef FRONTEND.
134 : */
135 :
136 : #ifndef FRONTEND
137 : static inline MemoryContext
6624 tgl 138 GIC 468890356 : MemoryContextSwitchTo(MemoryContext context)
139 : {
140 468890356 : MemoryContext old = CurrentMemoryContext;
141 :
142 468890356 : CurrentMemoryContext = context;
143 468890356 : return old;
144 : }
2118 tgl 145 ECB : #endif /* FRONTEND */
146 :
2961 147 : /* Registration of memory context reset/delete callbacks */
148 : extern void MemoryContextRegisterResetCallback(MemoryContext context,
1418 149 : MemoryContextCallback *cb);
2961 150 :
151 : /*
152 : * These are like standard strdup() except the copied string is
153 : * allocated in a context, not with malloc().
154 : */
155 : extern char *MemoryContextStrdup(MemoryContext context, const char *string);
156 : extern char *pstrdup(const char *in);
157 : extern char *pnstrdup(const char *in, Size len);
158 :
159 : extern char *pchomp(const char *in);
160 :
161 : /* sprintf into a palloc'd buffer --- these are in psprintf.c */
162 : extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);
163 : extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0);
164 :
165 : #endif /* PALLOC_H */
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