The Battle for Wesnoth  1.17.0-dev
lmem.cpp
Go to the documentation of this file.
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 
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 }
#define luaM_error(L)
Definition: lmem.h:17
l_mem GCdebt
Definition: lstate.h:223
l_noret luaG_runerror(lua_State *L, const char *fmt,...)
Definition: ldebug.cpp:767
void * luaM_growaux_(lua_State *L, void *block, int nelems, int *psize, int size_elems, int limit, const char *what)
Definition: lmem.cpp:79
lua_Alloc frealloc
Definition: lstate.h:220
static void * tryagain(lua_State *L, void *block, size_t osize, size_t nsize)
Definition: lmem.cpp:146
void luaM_free_(lua_State *L, void *block, size_t osize)
Definition: lmem.cpp:132
#define l_noret
Definition: llimits.h:178
#define G(L)
Definition: lstate.h:298
void * luaM_realloc_(lua_State *L, void *block, size_t osize, size_t nsize)
Definition: lmem.cpp:162
#define unlikely(x)
Definition: llimits.h:162
void * luaM_malloc_(lua_State *L, size_t size, int tag)
Definition: lmem.cpp:188
std::size_t size(const std::string &str)
Length in characters of a UTF-8 string.
Definition: unicode.cpp:86
void * ud
Definition: lstate.h:221
#define ttisnil(v)
Definition: lobject.h:171
#define MINSIZEARRAY
Definition: lmem.cpp:76
void * luaM_saferealloc_(lua_State *L, void *block, size_t osize, size_t nsize)
Definition: lmem.cpp:179
void * luaM_shrinkvector_(lua_State *L, void *block, int *size, int final_n, int size_elem)
Definition: lmem.cpp:110
static void block(LexState *ls)
Definition: lparser.cpp:1293
#define lua_assert(c)
Definition: llimits.h:101
TValue nilvalue
Definition: lstate.h:228
double g
Definition: astarsearch.cpp:64
#define firsttry(g, block, os, ns)
Definition: lmem.cpp:38
#define cast_sizet(i)
Definition: llimits.h:134
void luaC_fullgc(lua_State *L, int isemergency)
Definition: lgc.cpp:1703
l_noret luaM_toobig(lua_State *L)
Definition: lmem.cpp:124