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 */ 69 static 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 97 void *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 */ 128 void *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 /* }================================================================== */ 140 141 142 l_noret luaM_toobig (lua_State *L) { 143 luaG_runerror(L, "memory allocation error: block too big"); 144 } 145 146 147 /* 148 ** Free memory 149 */ 150 void 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 */ 162 static 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 */ 176 void *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 } 190 191 192 void *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 } 199 200 201 void *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 } 216