1/*
2** $Id: lmem.c $
3** Interface to Memory Manager
4** See Copyright Notice in lua.h
5*/
6
7#define lmem_c
8#define LUA_CORE
9
10#include "lprefix.h"
11
12
13#include <stddef.h>
14
15#include "lua.h"
16
17#include "ldebug.h"
18#include "ldo.h"
19#include "lgc.h"
20#include "lmem.h"
21#include "lobject.h"
22#include "lstate.h"
23
24
25
26/*
27** About the realloc function:
28** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
29** ('osize' is the old size, 'nsize' is the new size)
30**
31** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL.
32** Particularly, frealloc(ud, NULL, 0, 0) does nothing,
33** which is equivalent to free(NULL) in ISO C.
34**
35** - frealloc(ud, NULL, x, s) creates a new block of size 's'
36** (no matter 'x'). Returns NULL if it cannot create the new block.
37**
38** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from
39** size 'x' to size 'y'. Returns NULL if it cannot reallocate the
40** block to the new size.
41*/
42
43
44/*
45** Macro to call the allocation function.
46*/
47#define callfrealloc(g,block,os,ns) ((*g->frealloc)(g->ud, block, os, ns))
48
49
50/*
51** When an allocation fails, it will try again after an emergency
52** collection, except when it cannot run a collection. The GC should
53** not be called while the state is not fully built, as the collector
54** is not yet fully initialized. Also, it should not be called when
55** 'gcstopem' is true, because then the interpreter is in the middle of
56** a collection step.
57*/
58#define cantryagain(g) (completestate(g) && !g->gcstopem)
59
60
61
62
63#if defined(EMERGENCYGCTESTS)
64/*
65** First allocation will fail except when freeing a block (frees never
66** fail) and when it cannot try again; this fail will trigger 'tryagain'
67** and a full GC cycle at every allocation.
68*/
69static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
70 if (ns > 0 && cantryagain(g))
71 return NULL; /* fail */
72 else /* normal allocation */
73 return callfrealloc(g, block, os, ns);
74}
75#else
76#define firsttry(g,block,os,ns) callfrealloc(g, block, os, ns)
77#endif
78
79
80
81
82
83/*
84** {==================================================================
85** Functions to allocate/deallocate arrays for the Parser
86** ===================================================================
87*/
88
89/*
90** Minimum size for arrays during parsing, to avoid overhead of
91** reallocating to size 1, then 2, and then 4. All these arrays
92** will be reallocated to exact sizes or erased when parsing ends.
93*/
94#define MINSIZEARRAY 4
95
96
97void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize,
98 int size_elems, int limit, const char *what) {
99 void *newblock;
100 int size = *psize;
101 if (nelems + 1 <= size) /* does one extra element still fit? */
102 return block; /* nothing to be done */
103 if (size >= limit / 2) { /* cannot double it? */
104 if (l_unlikely(size >= limit)) /* cannot grow even a little? */
105 luaG_runerror(L, "too many %s (limit is %d)", what, limit);
106 size = limit; /* still have at least one free place */
107 }
108 else {
109 size *= 2;
110 if (size < MINSIZEARRAY)
111 size = MINSIZEARRAY; /* minimum size */
112 }
113 lua_assert(nelems + 1 <= size && size <= limit);
114 /* 'limit' ensures that multiplication will not overflow */
115 newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems,
116 cast_sizet(size) * size_elems);
117 *psize = size; /* update only when everything else is OK */
118 return newblock;
119}
120
121
122/*
123** In prototypes, the size of the array is also its number of
124** elements (to save memory). So, if it cannot shrink an array
125** to its number of elements, the only option is to raise an
126** error.
127*/
128void *luaM_shrinkvector_ (lua_State *L, void *block, int *size,
129 int final_n, int size_elem) {
130 void *newblock;
131 size_t oldsize = cast_sizet((*size) * size_elem);
132 size_t newsize = cast_sizet(final_n * size_elem);
133 lua_assert(newsize <= oldsize);
134 newblock = luaM_saferealloc_(L, block, oldsize, newsize);
135 *size = final_n;
136 return newblock;
137}
138
139/* }================================================================== */
140
141
142l_noret luaM_toobig (lua_State *L) {
143 luaG_runerror(L, "memory allocation error: block too big");
144}
145
146
147/*
148** Free memory
149*/
150void luaM_free_ (lua_State *L, void *block, size_t osize) {
151 global_State *g = G(L);
152 lua_assert((osize == 0) == (block == NULL));
153 callfrealloc(g, block, osize, 0);
154 g->GCdebt -= osize;
155}
156
157
158/*
159** In case of allocation fail, this function will do an emergency
160** collection to free some memory and then try the allocation again.
161*/
162static void *tryagain (lua_State *L, void *block,
163 size_t osize, size_t nsize) {
164 global_State *g = G(L);
165 if (cantryagain(g)) {
166 luaC_fullgc(L, 1); /* try to free some memory... */
167 return callfrealloc(g, block, osize, nsize); /* try again */
168 }
169 else return NULL; /* cannot run an emergency collection */
170}
171
172
173/*
174** Generic allocation routine.
175*/
176void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
177 void *newblock;
178 global_State *g = G(L);
179 lua_assert((osize == 0) == (block == NULL));
180 newblock = firsttry(g, block, osize, nsize);
181 if (l_unlikely(newblock == NULL && nsize > 0)) {
182 newblock = tryagain(L, block, osize, nsize);
183 if (newblock == NULL) /* still no memory? */
184 return NULL; /* do not update 'GCdebt' */
185 }
186 lua_assert((nsize == 0) == (newblock == NULL));
187 g->GCdebt = (g->GCdebt + nsize) - osize;
188 return newblock;
189}
190
191
192void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize,
193 size_t nsize) {
194 void *newblock = luaM_realloc_(L, block, osize, nsize);
195 if (l_unlikely(newblock == NULL && nsize > 0)) /* allocation failed? */
196 luaM_error(L);
197 return newblock;
198}
199
200
201void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
202 if (size == 0)
203 return NULL; /* that's all */
204 else {
205 global_State *g = G(L);
206 void *newblock = firsttry(g, NULL, tag, size);
207 if (l_unlikely(newblock == NULL)) {
208 newblock = tryagain(L, NULL, tag, size);
209 if (newblock == NULL)
210 luaM_error(L);
211 }
212 g->GCdebt += size;
213 return newblock;
214 }
215}