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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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13
Source/Modules/php.cxx
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@ -87,6 +87,15 @@ static String *fake_class_name() {
return result;
}
static String *swig_wrapped_interface_ce() {
static String *result = NULL;
if (!result) {
result = NewStringf("SWIG_Php_swig_wrapped_interface_ce");
Printf(s_oinit, " INIT_CLASS_ENTRY(%s, \"SWIG\\\\wrapped\", NULL);\n", result);
}
return result;
}
/* To reduce code size (generated and compiled) we only want to emit each
* different arginfo once, so we need to track which have been used.
*/
@ -163,12 +172,14 @@ static void SwigPHP_emit_pointer_type_registrations() {
while (ki.key) {
String *type = ki.key;
String *swig_wrapped = swig_wrapped_interface_ce();
Printf(s_creation, "/* class entry for pointer to %s */\n", type);
Printf(s_creation, "static zend_class_entry *SWIG_Php_ce_%s;\n\n", type);
Printf(s_oinit, " INIT_CLASS_ENTRY(internal_ce, \"%s\\\\%s\", NULL);\n", "SWIG", type);
Printf(s_oinit, " SWIG_Php_ce_%s = zend_register_internal_class(&internal_ce);\n", type);
Printf(s_oinit, " SWIG_Php_ce_%s->create_object = swig_ptr_object_new;\n", type);
Printv(s_oinit, " zend_do_implement_interface(SWIG_Php_ce_", type, ", &", swig_wrapped, ");\n", NIL);
Printf(s_oinit, " SWIG_TypeClientData(SWIGTYPE%s,SWIG_Php_ce_%s);\n", type, type);
Printf(s_oinit, "\n");
@ -1633,6 +1644,8 @@ public:
if (Getattr(n, "abstracts") && !GetFlag(n, "feature:notabstract")) {
Printf(s_oinit, " SWIG_Php_ce_%s->ce_flags |= ZEND_ACC_EXPLICIT_ABSTRACT_CLASS;\n", class_name);
}
String *swig_wrapped = swig_wrapped_interface_ce();
Printv(s_oinit, " zend_do_implement_interface(SWIG_Php_ce_", class_name, ", &", swig_wrapped, ");\n", NIL);
{
Node *node = NewHash();