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avoid warnings in macro 'luaM_reallocv' + comments

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Roberto Ierusalimschy 2014-10-08 17:25:51 -03:00
parent 65ec3379b1
commit ffe7401ceb
1 changed files with 15 additions and 9 deletions
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24
lmem.h
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@ -1,5 +1,5 @@
/*
** $Id: lmem.h,v 1.39 2012/11/14 17:21:34 roberto Exp roberto $
** $Id: lmem.h,v 1.40 2013/02/20 14:08:21 roberto Exp roberto $
** Interface to Memory Manager
** See Copyright Notice in lua.h
*/
@ -15,20 +15,26 @@
/*
** This macro avoids the runtime division MAX_SIZET/(e), as 'e' is
** always constant.
** The macro is somewhat complex to avoid warnings:
** +1 avoids warnings of "comparison has constant result";
** cast to 'void' avoids warnings of "value unused".
** This macro reallocs a vector 'b' from 'on' to 'n' elements, where
** each element has size 'e'. In case of arithmetic overflow of the
** product 'n'*'e', it raises an error (calling 'luaM_toobig'). 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_reallocv(L,b,on,n,e) \
(cast(void, \
(cast(size_t, (n)+1) > MAX_SIZET/(e)) ? (luaM_toobig(L), 0) : 0), \
(((sizeof(n) >= sizeof(size_t) && cast(size_t, (n)) + 1 > MAX_SIZET/(e)) \
? luaM_toobig(L) : cast_void(0)) , \
luaM_realloc_(L, (b), (on)*(e), (n)*(e)))
#define luaM_freemem(L, b, s) luaM_realloc_(L, (b), (s), 0)
#define luaM_free(L, b) luaM_realloc_(L, (b), sizeof(*(b)), 0)
#define luaM_freearray(L, b, n) luaM_reallocv(L, (b), n, 0, sizeof((b)[0]))
#define luaM_freearray(L, b, n) luaM_realloc_(L, (b), (n)*sizeof(*(b)), 0)
#define luaM_malloc(L,s) luaM_realloc_(L, NULL, 0, (s))
#define luaM_new(L,t) cast(t *, luaM_malloc(L, sizeof(t)))