commit ffe7401cebeab91ba21758773f590f52c12f6d4b
parent 65ec3379b10654f49b7faaf841b308b0cbb7b68b
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 8 Oct 2014 17:25:26 -0300
avoid warnings in macro 'luaM_reallocv' + comments
Diffstat:
| M | lmem.h | | | 24 | +++++++++++++++--------- |
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/lmem.h b/lmem.h
@@ -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)))
