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FFI Incompatible types when assigning to type 'void(*)()' from type 'void(*)()' #9090
Description
Description
It appears we're unable to assign a function pointer via FFI:
$ cat ffibug.c
#include <stdio.h>
void func() {
printf("hello\n");
}
void (*func_ptr)() = NULL;
void call_func() {
if (func_ptr != NULL) func_ptr();
}
$ gcc -shared -fPIC -o libffibug.so ffibug.c
$ php -v
PHP 8.2.0-dev (cli) (built: Jul 19 2022 20:25:19) (NTS DEBUG)
Copyright (c) The PHP Group
Zend Engine v4.2.0-dev, Copyright (c) Zend Technologies
$ php -a
Interactive shell
php > $ffi = FFI::cdef('void func(); void (*func_ptr)(); void call_func();', __DIR__ . '/libffibug.so');
php > $ffi->call_func();
php > $ffi->func_ptr = $ffi->func;
Warning: Uncaught FFI\Exception: Incompatible types when assigning to type 'void(*)()' from type 'void(*)()' in php shell code:1
Stack trace:
#0 {main}
thrown in php shell code on line 1
php >
The following patch seems to fix:
diff --git a/ext/ffi/ffi.c b/ext/ffi/ffi.c
index cb82c3a3c3..3cd568826f 100644
--- a/ext/ffi/ffi.c
+++ b/ext/ffi/ffi.c
@@ -267,7 +267,8 @@ static bool zend_ffi_is_compatible_type(zend_ffi_type *dst_type, zend_ffi_type *
dst_type = ZEND_FFI_TYPE(dst_type->pointer.type);
src_type = ZEND_FFI_TYPE(src_type->pointer.type);
if (dst_type->kind == ZEND_FFI_TYPE_VOID ||
- src_type->kind == ZEND_FFI_TYPE_VOID) {
+ src_type->kind == ZEND_FFI_TYPE_VOID ||
+ src_type->kind == dst_type->kind) {
return 1;
}
} else if (dst_type->kind == ZEND_FFI_TYPE_ARRAY &&$ php -a
Interactive shell
php > $ffi = FFI::cdef('void func(); void (*func_ptr)(); void call_func();', __DIR__ . '/libffibug.so');
php > $ffi->call_func();
php > $ffi->func_ptr = $ffi->func;
php > $ffi->call_func();
hello
php >
$
I'm not familiar with FFI internals so could use a review. FFI tests continue to pass at least. If it looks ok I can follow up with a PR + phpt.
PHP Version
HEAD
Operating System
Debian testing
Activity
cmb69 commentedon Jul 22, 2022
Hmm, I think we could do that, but that would allow to assign any function pointer to any other. So we would not only ignore the return and parameter types, but also the calling convention. That would seriously undermine the type safety of FFI. To wit:
If we want to support function pointer compatibility (what looks sensible), we should also check the details (
src_type->funcanddst_type->func).adsr commentedon Jul 22, 2022
Yes good idea @cmb69. I'll submit a PR incorporating that.
adsr commentedon Jul 22, 2022
#9107