Why can't I query local variables after OP_CALL?
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- Subject: Why can't I query local variables after OP_CALL?
- From: Andreas Falkenhahn <andreas@...>
- Date: 2019年8月16日 22:56:51 +0200
I wrote this C function to print the names of all local variables:
void dumplocals(lua_State *L) {
lua_Debug ar;
int level = 0, i;
const char *name;
if(lua_getstack(L, level, &ar) == 0) {
printf("Error\n");
return;
}
i = 0;
while((name = lua_getlocal(L, &ar, i + 1)) != NULL) {
printf("%s\n", name);
lua_pop(L, 1);
i++;
}
}
And this is the Lua code:
do
local a,b,c=1,2,3
print(a,b,c)
testfunc()
end
Note that testfunc() is a C function. Now I'd like to print the names of all local variables when testfunc() returns. That's why I have added a call to dumplocals() to lvm.c/luaV_execute() in the OP_CALL/OP_TAILCALL branch as follows:
firstResult = luaD_precall(L, ra);
if (firstResult) {
if (firstResult > L->top) { /* yield? */
lua_assert(L->ci->state == (CI_C | CI_YIELD));
(L->ci - 1)->u.l.savedpc = pc;
(L->ci - 1)->state = CI_SAVEDPC;
return NULL;
}
/* it was a C function (`precall' called it); adjust results */
luaD_poscall(L, nresults, firstResult);
if (nresults >= 0) L->top = L->ci->top;
// !!! THIS IS THE ONLY LINE I ADDED !!!
dumplocals(L);
}
Note that I'm still on Lua 5.0.
Now I'd expect dumplocals() to print
a
b
c
But it doesn't do that. Instead, lua_getlocal() in dumplocals() always returns NULL although there should be three local variables a,b,c. So I don't really understand why this doesn't work. Can anybody explain?
--
Best regards,
Andreas Falkenhahn mailto:andreas@falkenhahn.com