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[php] Allow testing if an object is SWIG-wrapped

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Since the switch to wrapping classes using PHP's C API, we now
internally need to be able to tell if a PHP object is of or derived
from a class that is wrapped by SWIG so we know if we can offset the
zend_object pointer to get to the swig_object_wrapper.  If we try to
do this to an object which isn't wrapped by SWIG then we invoke C/C++
undefined behaviour (and typically get a segmentation fault).

This check is implemented by having a SWIG\wrapped empty interface which
we make all SWIG-wrapped classes implement simply so we can test for it
to detect such classes.

Fixes #2125
This commit is contained in:
Olly Betts 2022-01-20 14:42:02 +13:00
commit c417250b4e
3 changed files with 35 additions and 4 deletions
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19
Lib/php/phprun.swg
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@ -93,6 +93,12 @@ static int default_error_code = E_ERROR;
#define SWIG_GetModule(clientdata) SWIG_Php_GetModule()
#define SWIG_SetModule(clientdata, pointer) SWIG_Php_SetModule(pointer, *(int*)clientdata)
static zend_class_entry SWIG_Php_swig_wrapped_interface_ce;
#if PHP_MAJOR_VERSION == 7
# define zend_class_implements_interface(C, I) instanceof_function_ex(C, I, 1)
#endif
/* used to wrap returned objects in so we know whether they are newobject
and need freeing, or not */
typedef struct {
@ -156,7 +162,18 @@ SWIG_ConvertPtrAndOwn(zval *z, void **ptr, swig_type_info *ty, int flags, swig_o
switch (Z_TYPE_P(z)) {
case IS_OBJECT: {
swig_object_wrapper *value = SWIG_Z_FETCH_OBJ_P(z);
zend_object *obj = Z_OBJ_P(z);
swig_object_wrapper *value;
if (ty && ty->clientdata == (void*)obj->ce) {
// Object is exactly the class asked for - this handles common cases cheaply,
// and in particular the PHP classes we use to wrap a pointer to a non-class.
} else if (!zend_class_implements_interface(obj->ce, &SWIG_Php_swig_wrapped_interface_ce)) {
// Not an object we've wrapped.
return -1;
}
/* convert and cast value->ptr from value->type to ptr as ty. */
value = swig_php_fetch_object(obj);
if (!ty) {
/* They don't care about the target type, so just pass on the pointer! */
*ptr = value->ptr;