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Added macro LUAI_STRICT_ADDRESS

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By default, the code assumes it is safe to use a dealocated pointer
as long as the code does not access it.
This commit is contained in:
Roberto Ierusalimschy 2025-02-18 17:02:32 -03:00
commit cd38fe8cf3
2 changed files with 22 additions and 10 deletions

28
ldo.c
View file

@ -192,14 +192,19 @@ TStatus luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
/*
** In ISO C, any pointer use after the pointer has been deallocated is
** undefined behavior. So, before a stack reallocation, all pointers are
** changed to offsets, and after the reallocation they are changed back
** to pointers. As during the reallocation the pointers are invalid, the
** reallocation cannot run emergency collections.
**
** undefined behavior. So, before a stack reallocation, all pointers
** should be changed to offsets, and after the reallocation they should
** be changed back to pointers. As during the reallocation the pointers
** are invalid, the reallocation cannot run emergency collections.
** Alternatively, we can use the old address after the deallocation.
** That is not strict ISO C, but seems to work fine everywhere.
** The following macro chooses how strict is the code.
*/
#if !defined(LUAI_STRICT_ADDRESS)
#define LUAI_STRICT_ADDRESS 0
#endif
#if 1
#if LUAI_STRICT_ADDRESS
/*
** Change all pointers to the stack into offsets.
*/
@ -238,12 +243,16 @@ static void correctstack (lua_State *L, StkId oldstack) {
#else
/*
** Alternatively, we can use the old address after the deallocation.
** That is not strict ISO C, but seems to work fine everywhere.
** Assume that it is fine to use an address after its deallocation,
** as long as we do not dereference it.
*/
static void relstack (lua_State *L) { UNUSED(L); }
static void relstack (lua_State *L) { UNUSED(L); } /* do nothing */
/*
** Correct pointers into 'oldstack' to point into 'L->stack'.
*/
static void correctstack (lua_State *L, StkId oldstack) {
CallInfo *ci;
UpVal *up;
@ -261,7 +270,6 @@ static void correctstack (lua_State *L, StkId oldstack) {
ci->u.l.trap = 1; /* signal to update 'trap' in 'luaV_execute' */
}
}
#endif

4
ltests.h
View file

@ -44,6 +44,10 @@
#define LUA_RAND32
/* test stack reallocation with strict address use */
#define LUAI_STRICT_ADDRESS 1
/* memory-allocator control variables */
typedef struct Memcontrol {
int failnext;