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Save stack space while handling errors

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Because error handling (luaG_errormsg) uses slots from EXTRA_STACK,
and some errors can recur (e.g., string overflow while creating an
error message in 'luaG_runerror', or a C-stack overflow before calling
the message handler), the code should use stack slots with parsimony.

This commit fixes the bug "Lua-stack overflow when C stack overflows
while handling an error".
This commit is contained in:
Roberto Ierusalimschy 2022-05-20 13:14:33 -03:00
parent e435aaabef
commit 42d40581dd
2 changed files with 8 additions and 3 deletions
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5
ldebug.c
View File

@ -824,8 +824,11 @@ l_noret luaG_runerror (lua_State *L, const char *fmt, ...) {
va_start(argp, fmt); va_start(argp, fmt);
msg = luaO_pushvfstring(L, fmt, argp); /* format message */ msg = luaO_pushvfstring(L, fmt, argp); /* format message */
va_end(argp); va_end(argp);
if (isLua(ci)) /* if Lua function, add source:line information */ if (isLua(ci)) { /* if Lua function, add source:line information */
luaG_addinfo(L, msg, ci_func(ci)->p->source, getcurrentline(ci)); luaG_addinfo(L, msg, ci_func(ci)->p->source, getcurrentline(ci));
setobjs2s(L, L->top - 2, L->top - 1); /* remove 'msg' from the stack */
L->top--;
}
luaG_errormsg(L); luaG_errormsg(L);
} }

6
lvm.c
View File

@ -656,8 +656,10 @@ void luaV_concat (lua_State *L, int total) {
/* collect total length and number of strings */ /* collect total length and number of strings */
for (n = 1; n < total && tostring(L, s2v(top - n - 1)); n++) { for (n = 1; n < total && tostring(L, s2v(top - n - 1)); n++) {
size_t l = vslen(s2v(top - n - 1)); size_t l = vslen(s2v(top - n - 1));
if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) {
L->top = top - total; /* pop strings to avoid wasting stack */
luaG_runerror(L, "string length overflow"); luaG_runerror(L, "string length overflow");
}
tl += l; tl += l;
} }
if (tl <= LUAI_MAXSHORTLEN) { /* is result a short string? */ if (tl <= LUAI_MAXSHORTLEN) { /* is result a short string? */
@ -672,7 +674,7 @@ void luaV_concat (lua_State *L, int total) {
setsvalue2s(L, top - n, ts); /* create result */ setsvalue2s(L, top - n, ts); /* create result */
} }
total -= n-1; /* got 'n' strings to create 1 new */ total -= n-1; /* got 'n' strings to create 1 new */
L->top -= n-1; /* popped 'n' strings and pushed one */ L->top = top - (n - 1); /* popped 'n' strings and pushed one */
} while (total > 1); /* repeat until only 1 result left */ } while (total > 1); /* repeat until only 1 result left */
} }