Detect rehash in array-backed hashes #13919
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hash.c
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| int status = (*arg->func)((VALUE)key, (VALUE)value, arg->arg); | ||
| /* TODO: rehash check? rb_raise(rb_eRuntimeError, "rehash occurred during iteration"); */ | ||
| if (!RHASH_AR_TABLE_P(arg->hash) || RHASH_AR_TABLE(arg->hash) != tbl) { |
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I forget what happens on rehash, but RHASH_AR_TABLE(arg->hash) != tbl is correct checking?
hash.c
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| int status = (*arg->func)((VALUE)key, (VALUE)value, arg->arg); | ||
| /* TODO: rehash check? rb_raise(rb_eRuntimeError, "rehash occurred during iteration"); */ | ||
| if (!RHASH_AR_TABLE_P(arg->hash) || RHASH_AR_TABLE(arg->hash) != tbl) { |
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I know this is copying from similar code using RHASH_ST_TABLE, but that check might actually never trigger. RHASH_ST_TABLE() just adds an offset to the argument, so for the same hash, it's always going to be the same. arg->hash is never going to be changed by the callback, so that check will always be false.
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I changed this condition to check if the bound increases. That should work, right?
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@ko1 is this check and the on for ST table meant to be a debug assert? Seems like it's not possible to accurately check for rehash here efficiently. Maybe we should just remove the code and TODO, or turn them into st_table *tbl = RHASH_ST_TABLE(arg->hash);
int status = (*arg->func)((VALUE)key, (VALUE)value, arg->arg);
if (RHASH_ST_TABLE(arg->hash) != tbl) {
rb_raise(rb_eRuntimeError, "rehash occurred during iteration");
}With recent changes it never raises: static inline st_table *
RHASH_ST_TABLE(VALUE h)
{
return (st_table *)((uintptr_t)h + sizeof(struct RHash));
}Also, Hash#rehash disallows running while iterating, so it's unclear how these checks could fail in practice: if (hash_iterating_p(hash)) {
rb_raise(rb_eRuntimeError, "rehash during iteration");
} |
+1 for removing the code and TODO. |
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Okay, I've removed the code I added and the TODO. Would you like me to squash this into a single commit or will you squash when you merge? |
Added safeguards for array-backed hashes by storing the table pointer and bound in
hash_foreach_argand checking them during iteration to raise an exception if a rehash occurs.Fixed TODO added in 2018 by @ko1.