1 /* $NetBSD: lmem.c,v 1.11 2023/06/08 21:12:08 nikita Exp $ */
2
3 /*
4 ** Id: lmem.c
5 ** Interface to Memory Manager
6 ** See Copyright Notice in lua.h
7 */
8
9 #define lmem_c
10 #define LUA_CORE
11
12 #include "lprefix.h"
13
14
15 #ifndef _KERNEL
16 #include <stddef.h>
17 #endif /* _KERNEL */
18
19 #include "lua.h"
20
21 #include "ldebug.h"
22 #include "ldo.h"
23 #include "lgc.h"
24 #include "lmem.h"
25 #include "lobject.h"
26 #include "lstate.h"
27
28
29
30 /*
31 ** About the realloc function:
32 ** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
33 ** ('osize' is the old size, 'nsize' is the new size)
34 **
35 ** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL.
36 ** Particularly, frealloc(ud, NULL, 0, 0) does nothing,
37 ** which is equivalent to free(NULL) in ISO C.
38 **
39 ** - frealloc(ud, NULL, x, s) creates a new block of size 's'
40 ** (no matter 'x'). Returns NULL if it cannot create the new block.
41 **
42 ** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from
43 ** size 'x' to size 'y'. Returns NULL if it cannot reallocate the
44 ** block to the new size.
45 */
46
47
48 /*
49 ** Macro to call the allocation function.
50 */
51 #define callfrealloc(g,block,os,ns) ((*g->frealloc)(g->ud, block, os, ns))
52
53
54 /*
55 ** When an allocation fails, it will try again after an emergency
56 ** collection, except when it cannot run a collection. The GC should
57 ** not be called while the state is not fully built, as the collector
58 ** is not yet fully initialized. Also, it should not be called when
59 ** 'gcstopem' is true, because then the interpreter is in the middle of
60 ** a collection step.
61 */
62 #define cantryagain(g) (completestate(g) && !g->gcstopem)
63
64
65
66
67 #if defined(EMERGENCYGCTESTS)
68 /*
69 ** First allocation will fail except when freeing a block (frees never
70 ** fail) and when it cannot try again; this fail will trigger 'tryagain'
71 ** and a full GC cycle at every allocation.
72 */
firsttry(global_State * g,void * block,size_t os,size_t ns)73 static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
74 if (ns > 0 && cantryagain(g))
75 return NULL; /* fail */
76 else /* normal allocation */
77 return callfrealloc(g, block, os, ns);
78 }
79 #else
80 #define firsttry(g,block,os,ns) callfrealloc(g, block, os, ns)
81 #endif
82
83
84
85
86
87 /*
88 ** {==================================================================
89 ** Functions to allocate/deallocate arrays for the Parser
90 ** ===================================================================
91 */
92
93 /*
94 ** Minimum size for arrays during parsing, to avoid overhead of
95 ** reallocating to size 1, then 2, and then 4. All these arrays
96 ** will be reallocated to exact sizes or erased when parsing ends.
97 */
98 #define MINSIZEARRAY 4
99
100
luaM_growaux_(lua_State * L,void * block,int nelems,int * psize,int size_elems,int limit,const char * what)101 void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize,
102 int size_elems, int limit, const char *what) {
103 void *newblock;
104 int size = *psize;
105 if (nelems + 1 <= size) /* does one extra element still fit? */
106 return block; /* nothing to be done */
107 if (size >= limit / 2) { /* cannot double it? */
108 if (l_unlikely(size >= limit)) /* cannot grow even a little? */
109 luaG_runerror(L, "too many %s (limit is %d)", what, limit);
110 size = limit; /* still have at least one free place */
111 }
112 else {
113 size *= 2;
114 if (size < MINSIZEARRAY)
115 size = MINSIZEARRAY; /* minimum size */
116 }
117 lua_assert(nelems + 1 <= size && size <= limit);
118 /* 'limit' ensures that multiplication will not overflow */
119 newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems,
120 cast_sizet(size) * size_elems);
121 *psize = size; /* update only when everything else is OK */
122 return newblock;
123 }
124
125
126 /*
127 ** In prototypes, the size of the array is also its number of
128 ** elements (to save memory). So, if it cannot shrink an array
129 ** to its number of elements, the only option is to raise an
130 ** error.
131 */
luaM_shrinkvector_(lua_State * L,void * block,int * size,int final_n,int size_elem)132 void *luaM_shrinkvector_ (lua_State *L, void *block, int *size,
133 int final_n, int size_elem) {
134 void *newblock;
135 size_t oldsize = cast_sizet((*size) * size_elem);
136 size_t newsize = cast_sizet(final_n * size_elem);
137 lua_assert(newsize <= oldsize);
138 newblock = luaM_saferealloc_(L, block, oldsize, newsize);
139 *size = final_n;
140 return newblock;
141 }
142
143 /* }================================================================== */
144
145
luaM_toobig(lua_State * L)146 l_noret luaM_toobig (lua_State *L) {
147 luaG_runerror(L, "memory allocation error: block too big");
148 }
149
150
151 /*
152 ** Free memory
153 */
luaM_free_(lua_State * L,void * block,size_t osize)154 void luaM_free_ (lua_State *L, void *block, size_t osize) {
155 global_State *g = G(L);
156 lua_assert((osize == 0) == (block == NULL));
157 callfrealloc(g, block, osize, 0);
158 g->GCdebt -= osize;
159 }
160
161
162 /*
163 ** In case of allocation fail, this function will do an emergency
164 ** collection to free some memory and then try the allocation again.
165 */
tryagain(lua_State * L,void * block,size_t osize,size_t nsize)166 static void *tryagain (lua_State *L, void *block,
167 size_t osize, size_t nsize) {
168 global_State *g = G(L);
169 if (cantryagain(g)) {
170 luaC_fullgc(L, 1); /* try to free some memory... */
171 return callfrealloc(g, block, osize, nsize); /* try again */
172 }
173 else return NULL; /* cannot run an emergency collection */
174 }
175
176
177 /*
178 ** Generic allocation routine.
179 */
luaM_realloc_(lua_State * L,void * block,size_t osize,size_t nsize)180 void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
181 void *newblock;
182 global_State *g = G(L);
183 lua_assert((osize == 0) == (block == NULL));
184 newblock = firsttry(g, block, osize, nsize);
185 if (l_unlikely(newblock == NULL && nsize > 0)) {
186 newblock = tryagain(L, block, osize, nsize);
187 if (newblock == NULL) /* still no memory? */
188 return NULL; /* do not update 'GCdebt' */
189 }
190 lua_assert((nsize == 0) == (newblock == NULL));
191 g->GCdebt = (g->GCdebt + nsize) - osize;
192 return newblock;
193 }
194
195
luaM_saferealloc_(lua_State * L,void * block,size_t osize,size_t nsize)196 void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize,
197 size_t nsize) {
198 void *newblock = luaM_realloc_(L, block, osize, nsize);
199 if (l_unlikely(newblock == NULL && nsize > 0)) /* allocation failed? */
200 luaM_error(L);
201 return newblock;
202 }
203
204
luaM_malloc_(lua_State * L,size_t size,int tag)205 void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
206 if (size == 0)
207 return NULL; /* that's all */
208 else {
209 global_State *g = G(L);
210 void *newblock = firsttry(g, NULL, tag, size);
211 if (l_unlikely(newblock == NULL)) {
212 newblock = tryagain(L, NULL, tag, size);
213 if (newblock == NULL)
214 luaM_error(L);
215 }
216 g->GCdebt += size;
217 return newblock;
218 }
219 }
220