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 #if defined(EMERGENCYGCTESTS) 26 /* 27 ** First allocation will fail whenever not building initial state 28 ** and not shrinking a block. (This fail will trigger 'tryagain' and 29 ** a full GC cycle at every allocation.) 30 */ 31 static void *firsttry (global_State *g, void *block, size_t os, size_t ns) { 32 if (ttisnil(&g->nilvalue) && ns > os) 33 return NULL; /* fail */ 34 else /* normal allocation */ 35 return (*g->frealloc)(g->ud, block, os, ns); 36 } 37 #else 38 #define firsttry(g,block,os,ns) ((*g->frealloc)(g->ud, block, os, ns)) 39 #endif 40 41 42 43 44 45 /* 46 ** About the realloc function: 47 ** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize); 48 ** ('osize' is the old size, 'nsize' is the new size) 49 ** 50 ** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL. 51 ** Particularly, frealloc(ud, NULL, 0, 0) does nothing, 52 ** which is equivalent to free(NULL) in ISO C. 53 ** 54 ** - frealloc(ud, NULL, x, s) creates a new block of size 's' 55 ** (no matter 'x'). Returns NULL if it cannot create the new block. 56 ** 57 ** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from 58 ** size 'x' to size 'y'. Returns NULL if it cannot reallocate the 59 ** block to the new size. 60 */ 61 62 63 64 65 /* 66 ** {================================================================== 67 ** Functions to allocate/deallocate arrays for the Parser 68 ** =================================================================== 69 */ 70 71 /* 72 ** Minimum size for arrays during parsing, to avoid overhead of 73 ** reallocating to size 1, then 2, and then 4. All these arrays 74 ** will be reallocated to exact sizes or erased when parsing ends. 75 */ 76 #define MINSIZEARRAY 4 77 78 79 void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize, 80 int size_elems, int limit, const char *what) { 81 void *newblock; 82 int size = *psize; 83 if (nelems + 1 <= size) /* does one extra element still fit? */ 84 return block; /* nothing to be done */ 85 if (size >= limit / 2) { /* cannot double it? */ 86 if (unlikely(size >= limit)) /* cannot grow even a little? */ 87 luaG_runerror(L, "too many %s (limit is %d)", what, limit); 88 size = limit; /* still have at least one free place */ 89 } 90 else { 91 size *= 2; 92 if (size < MINSIZEARRAY) 93 size = MINSIZEARRAY; /* minimum size */ 94 } 95 lua_assert(nelems + 1 <= size && size <= limit); 96 /* 'limit' ensures that multiplication will not overflow */ 97 newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems, 98 cast_sizet(size) * size_elems); 99 *psize = size; /* update only when everything else is OK */ 100 return newblock; 101 } 102 103 104 /* 105 ** In prototypes, the size of the array is also its number of 106 ** elements (to save memory). So, if it cannot shrink an array 107 ** to its number of elements, the only option is to raise an 108 ** error. 109 */ 110 void *luaM_shrinkvector_ (lua_State *L, void *block, int *size, 111 int final_n, int size_elem) { 112 void *newblock; 113 size_t oldsize = cast_sizet((*size) * size_elem); 114 size_t newsize = cast_sizet(final_n * size_elem); 115 lua_assert(newsize <= oldsize); 116 newblock = luaM_saferealloc_(L, block, oldsize, newsize); 117 *size = final_n; 118 return newblock; 119 } 120 121 /* }================================================================== */ 122 123 124 l_noret luaM_toobig (lua_State *L) { 125 luaG_runerror(L, "memory allocation error: block too big"); 126 } 127 128 129 /* 130 ** Free memory 131 */ 132 void luaM_free_ (lua_State *L, void *block, size_t osize) { 133 global_State *g = G(L); 134 lua_assert((osize == 0) == (block == NULL)); 135 (*g->frealloc)(g->ud, block, osize, 0); 136 g->GCdebt -= osize; 137 } 138 139 140 /* 141 ** In case of allocation fail, this function will call the GC to try 142 ** to free some memory and then try the allocation again. 143 ** (It should not be called when shrinking a block, because then the 144 ** interpreter may be in the middle of a collection step.) 145 */ 146 static void *tryagain (lua_State *L, void *block, 147 size_t osize, size_t nsize) { 148 global_State *g = G(L); 149 if (ttisnil(&g->nilvalue)) { /* is state fully build? */ 150 luaC_fullgc(L, 1); /* try to free some memory... */ 151 return (*g->frealloc)(g->ud, block, osize, nsize); /* try again */ 152 } 153 else return NULL; /* cannot free any memory without a full state */ 154 } 155 156 157 /* 158 ** Generic allocation routine. 159 ** If allocation fails while shrinking a block, do not try again; the 160 ** GC shrinks some blocks and it is not reentrant. 161 */ 162 void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) { 163 void *newblock; 164 global_State *g = G(L); 165 lua_assert((osize == 0) == (block == NULL)); 166 newblock = firsttry(g, block, osize, nsize); 167 if (unlikely(newblock == NULL && nsize > 0)) { 168 if (nsize > osize) /* not shrinking a block? */ 169 newblock = tryagain(L, block, osize, nsize); 170 if (newblock == NULL) /* still no memory? */ 171 return NULL; /* do not update 'GCdebt' */ 172 } 173 lua_assert((nsize == 0) == (newblock == NULL)); 174 g->GCdebt = (g->GCdebt + nsize) - osize; 175 return newblock; 176 } 177 178 179 void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize, 180 size_t nsize) { 181 void *newblock = luaM_realloc_(L, block, osize, nsize); 182 if (unlikely(newblock == NULL && nsize > 0)) /* allocation failed? */ 183 luaM_error(L); 184 return newblock; 185 } 186 187 188 void *luaM_malloc_ (lua_State *L, size_t size, int tag) { 189 if (size == 0) 190 return NULL; /* that's all */ 191 else { 192 global_State *g = G(L); 193 void *newblock = firsttry(g, NULL, tag, size); 194 if (unlikely(newblock == NULL)) { 195 newblock = tryagain(L, NULL, tag, size); 196 if (newblock == NULL) 197 luaM_error(L); 198 } 199 g->GCdebt += size; 200 return newblock; 201 } 202 } 203