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Add alternative to zend_string_dup for persistent strings #9768

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Add alternative to zend_string_dup for persistent strings #9768

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13 changes: 13 additions & 0 deletions Zend/zend_string.h
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Original file line number Diff line number Diff line change
Expand Up @@ -195,9 +195,22 @@ static zend_always_inline zend_string *zend_string_copy(zend_string *s)
return s;
}

static zend_always_inline zend_string *zend_string_dup_safe(zend_string *s, bool persistent)
{
if (ZSTR_IS_INTERNED(s) && (!persistent || (GC_FLAGS(s) & IS_STR_PERSISTENT))) {
return s;
} else {
return zend_string_init(ZSTR_VAL(s), ZSTR_LEN(s), persistent);
}
}

/* Callers should use PHP 8.2's definition of zend_string_dup_safe instead,
if they need a temporary or interned persistent string
and aren't sure if it might be a temporary (allocated with emalloc) interned string. */
static zend_always_inline zend_string *zend_string_dup(zend_string *s, bool persistent)
{
if (ZSTR_IS_INTERNED(s)) {
ZEND_ASSERT(!persistent || (GC_FLAGS(s) & (IS_STR_PERSISTENT|IS_STR_PERMANENT)));
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It is my understanding that ZSTR_IS_INTERNED(s) implies IS_STR_PERSISTENT|IS_STR_PERMANENT, unless the string was interned during a request, which is not supposed to happen except when using dl(), according to

php-src/Zend/zend_string.c

Lines 254 to 260 in 33dd226

#if ZEND_RC_DEBUG
if (zend_rc_debug) {
/* PHP shouldn't create persistent interned string during request,
* but at least dl() may do this */
ZEND_ASSERT(!(GC_FLAGS(str) & GC_PERSISTENT));
}
#endif

Are there other cases where ZSTR_IS_INTERNED(s) does not imply IS_STR_PERSISTENT|IS_STR_PERMANENT?

Since this targets master, we might as well change the behavior of zend_string_dup() directly?

return s;
} else {
return zend_string_init(ZSTR_VAL(s), ZSTR_LEN(s), persistent);
Expand Down