12.2.2.1.18. LMEM¶
12.2.2.1.18.1. lmem.h¶
/*
** $Id: lmem.h $
** Interface to Memory Manager
** See Copyright Notice in lua.h
*/
#ifndef lmem_h
#define lmem_h
#include <stddef.h>
#include "llimits.h"
#include "lua.h"
#include "_native_lua_config.h" /* native Lua */
#define luaM_error(L) luaD_throw(L, LUA_ERRMEM)
/*
** This macro tests whether it is safe to multiply 'n' by the size of
** type 't' without overflows. Because 'e' is always constant, it avoids
** the runtime division MAX_SIZET/(e).
** (The macro is somewhat complex to avoid warnings: The 'sizeof'
** comparison avoids a runtime comparison when overflow cannot occur.
** The compiler should be able to optimize the real test by itself, but
** when it does it, it may give a warning about "comparison is always
** false due to limited range of data type"; the +1 tricks the compiler,
** avoiding this warning but also this optimization.)
*/
#define luaM_testsize(n,e) \
(sizeof(n) >= sizeof(size_t) && cast_sizet((n)) + 1 > MAX_SIZET/(e))
#define luaM_checksize(L,n,e) \
(luaM_testsize(n,e) ? luaM_toobig(L) : cast_void(0))
/*
** Computes the minimum between 'n' and 'MAX_SIZET/sizeof(t)', so that
** the result is not larger than 'n' and cannot overflow a 'size_t'
** when multiplied by the size of type 't'. (Assumes that 'n' is an
** 'int' or 'unsigned int' and that 'int' is not larger than 'size_t'.)
*/
#define luaM_limitN(n,t) \
((cast_sizet(n) <= MAX_SIZET/sizeof(t)) ? (n) : \
cast_uint((MAX_SIZET/sizeof(t))))
/*
** Arrays of chars do not need any test
*/
#define luaM_reallocvchar(L,b,on,n) \
cast_charp(luaM_saferealloc_(L, (b), (on)*sizeof(char), (n)*sizeof(char)))
#define luaM_freemem(L, b, s) luaM_free_(L, (b), (s))
#define luaM_free(L, b) luaM_free_(L, (b), sizeof(*(b)))
#define luaM_freearray(L, b, n) luaM_free_(L, (b), (n)*sizeof(*(b)))
#define luaM_new(L,t) cast(t*, luaM_malloc_(L, sizeof(t), 0))
#define luaM_newvector(L,n,t) cast(t*, luaM_malloc_(L, (n)*sizeof(t), 0))
#define luaM_newvectorchecked(L,n,t) \
(luaM_checksize(L,n,sizeof(t)), luaM_newvector(L,n,t))
#define luaM_newobject(L,tag,s) luaM_malloc_(L, (s), tag)
#define luaM_growvector(L,v,nelems,size,t,limit,e) \
((v)=cast(t *, luaM_growaux_(L,v,nelems,&(size),sizeof(t), \
luaM_limitN(limit,t),e)))
#define luaM_reallocvector(L, v,oldn,n,t) \
(cast(t *, luaM_realloc_(L, v, cast_sizet(oldn) * sizeof(t), \
cast_sizet(n) * sizeof(t))))
#define luaM_shrinkvector(L,v,size,fs,t) \
((v)=cast(t *, luaM_shrinkvector_(L, v, &(size), fs, sizeof(t))))
LUAI_FUNC l_noret luaM_toobig (lua_State *L);
/* not to be called directly */
LUAI_FUNC void *luaM_realloc_ (lua_State *L, void *block, size_t oldsize,
size_t size);
LUAI_FUNC void *luaM_saferealloc_ (lua_State *L, void *block, size_t oldsize,
size_t size);
LUAI_FUNC void luaM_free_ (lua_State *L, void *block, size_t osize);
LUAI_FUNC void *luaM_growaux_ (lua_State *L, void *block, int nelems,
int *size, int size_elem, int limit,
const char *what);
LUAI_FUNC void *luaM_shrinkvector_ (lua_State *L, void *block, int *nelem,
int final_n, int size_elem);
LUAI_FUNC void *luaM_malloc_ (lua_State *L, size_t size, int tag);
#endif
12.2.2.1.18.2. lmem.c¶
/*
** $Id: lmem.c $
** Interface to Memory Manager
** See Copyright Notice in lua.h
*/
#define lmem_c
#define LUA_CORE
#include "lprefix.h"
#include <stddef.h>
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#if defined(HARDMEMTESTS)
/*
** First allocation will fail whenever not building initial state
** and not shrinking a block. (This fail will trigger 'tryagain' and
** a full GC cycle at every allocation.)
*/
static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
if (ttisnil(&g->nilvalue) && ns > os)
return NULL; /* fail */
else /* normal allocation */
return (*g->frealloc)(g->ud, block, os, ns);
}
#else
#define firsttry(g,block,os,ns) ((*g->frealloc)(g->ud, block, os, ns))
#endif
/*
** About the realloc function:
** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
** ('osize' is the old size, 'nsize' is the new size)
**
** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL.
** Particularly, frealloc(ud, NULL, 0, 0) does nothing,
** which is equivalent to free(NULL) in ISO C.
**
** - frealloc(ud, NULL, x, s) creates a new block of size 's'
** (no matter 'x'). Returns NULL if it cannot create the new block.
**
** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from
** size 'x' to size 'y'. Returns NULL if it cannot reallocate the
** block to the new size.
*/
/*
** {==================================================================
** Functions to allocate/deallocate arrays for the Parser
** ===================================================================
*/
/*
** Minimum size for arrays during parsing, to avoid overhead of
** reallocating to size 1, then 2, and then 4. All these arrays
** will be reallocated to exact sizes or erased when parsing ends.
*/
#define MINSIZEARRAY 4
void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize,
int size_elems, int limit, const char *what) {
void *newblock;
int size = *psize;
if (nelems + 1 <= size) /* does one extra element still fit? */
return block; /* nothing to be done */
if (size >= limit / 2) { /* cannot double it? */
if (unlikely(size >= limit)) /* cannot grow even a little? */
luaG_runerror(L, "too many %s (limit is %d)", what, limit);
size = limit; /* still have at least one free place */
}
else {
size *= 2;
if (size < MINSIZEARRAY)
size = MINSIZEARRAY; /* minimum size */
}
lua_assert(nelems + 1 <= size && size <= limit);
/* 'limit' ensures that multiplication will not overflow */
newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems,
cast_sizet(size) * size_elems);
*psize = size; /* update only when everything else is OK */
return newblock;
}
/*
** In prototypes, the size of the array is also its number of
** elements (to save memory). So, if it cannot shrink an array
** to its number of elements, the only option is to raise an
** error.
*/
void *luaM_shrinkvector_ (lua_State *L, void *block, int *size,
int final_n, int size_elem) {
void *newblock;
size_t oldsize = cast_sizet((*size) * size_elem);
size_t newsize = cast_sizet(final_n * size_elem);
lua_assert(newsize <= oldsize);
newblock = luaM_saferealloc_(L, block, oldsize, newsize);
*size = final_n;
return newblock;
}
/* }================================================================== */
l_noret luaM_toobig (lua_State *L) {
luaG_runerror(L, "memory allocation error: block too big");
}
/*
** Free memory
*/
void luaM_free_ (lua_State *L, void *block, size_t osize) {
global_State *g = G(L);
lua_assert((osize == 0) == (block == NULL));
(*g->frealloc)(g->ud, block, osize, 0);
g->GCdebt -= osize;
}
/*
** In case of allocation fail, this function will call the GC to try
** to free some memory and then try the allocation again.
** (It should not be called when shrinking a block, because then the
** interpreter may be in the middle of a collection step.)
*/
static void *tryagain (lua_State *L, void *block,
size_t osize, size_t nsize) {
global_State *g = G(L);
if (ttisnil(&g->nilvalue)) { /* is state fully build? */
luaC_fullgc(L, 1); /* try to free some memory... */
return (*g->frealloc)(g->ud, block, osize, nsize); /* try again */
}
else return NULL; /* cannot free any memory without a full state */
}
/*
** Generic allocation routine.
** If allocation fails while shrinking a block, do not try again; the
** GC shrinks some blocks and it is not reentrant.
*/
void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
void *newblock;
global_State *g = G(L);
lua_assert((osize == 0) == (block == NULL));
newblock = firsttry(g, block, osize, nsize);
if (unlikely(newblock == NULL && nsize > 0)) {
if (nsize > osize) /* not shrinking a block? */
newblock = tryagain(L, block, osize, nsize);
if (newblock == NULL) /* still no memory? */
return NULL; /* do not update 'GCdebt' */
}
lua_assert((nsize == 0) == (newblock == NULL));
g->GCdebt = (g->GCdebt + nsize) - osize;
return newblock;
}
void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize,
size_t nsize) {
void *newblock = luaM_realloc_(L, block, osize, nsize);
if (unlikely(newblock == NULL && nsize > 0)) /* allocation failed? */
luaM_error(L);
return newblock;
}
void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
if (size == 0)
return NULL; /* that's all */
else {
global_State *g = G(L);
void *newblock = firsttry(g, NULL, tag, size);
if (unlikely(newblock == NULL)) {
newblock = tryagain(L, NULL, tag, size);
if (newblock == NULL)
luaM_error(L);
}
g->GCdebt += size;
return newblock;
}
}
