Can anyone help me with C macro? See full descript...

# kotlin-native

[rjhdby]

Can anyone help me with C macro?
See full description in thread.

[rjhdby]

Docs describe usage like:

headers = library/base.h

---

static inline int foo(int arg) {
    return FOO(arg);
}

My code.

Macro definition in external .h file

#define INI_STR(name) zend_ini_string_ex((name), sizeof(name)-1, 0, NULL)

Definition in .def file

static inline char* php_helper_ini_string(char* arg) {
    return INI_STR(arg);
}

Using in .kt

fun getStringIni(name:String) = php_helper_ini_string(name.cstr)?.toKString()?:"WARRRRGGGGHHHHH"

In fact, this code always return NULL (It is default behavior of zend_ini_string_ex for unknown argument.)

If I explict writing return INI_STR("somename"); in .def, then result is correct.

What I doing wrong?

[msink]

sizeof(char*) == 8 (on 64bit system) so you always use first 7 chars.
It should be something like this:

static inline char* php_helper_ini_string(char* name) {
    return zend_ini_string_ex(name, strlen(name), 0, NULL);
}

[rjhdby]

Unfortunately, in this case I need to use macro. Because of backward compatibility.
Do you have any suggestions about avoid this problem?

[msink]

That macro assumes C string constant as parameter, so you cannot use Kotlin string constant - it is not constant in C.

[msink]

If you want to pass stable pointer to C string from Kotlin, I know only one way: add in`.def`
noStringConversion = php_helper_ini_string

[msink]

Then from Kotlin you can call it as php_helper_ini_string(immutableBinaryBlobOf('A'.toShort, 0).asCPointer(0))

[msink]

But it is ImmutableBinaryBlob, not String.

[svyatoslav.scherbina]

In fact, this code always return NULL (It is default behavior of zend_ini_string_ex for unknown argument.)

What do you mean by “unknown argument”?

[msink]

ZEND_API char *zend_ini_string_ex(char *name, size_t name_length, int orig, zend_bool *exists)
{
	zend_ini_entry *ini_entry;

	ini_entry = zend_hash_str_find_ptr(EG(ini_directives), name, name_length);
	if (ini_entry) {
		if (exists) {
			*exists = 1;
		}

		if (orig && ini_entry->modified) {
			return ini_entry->orig_value ? ZSTR_VAL(ini_entry->orig_value) : NULL;
		} else {
			return ini_entry->value ? ZSTR_VAL(ini_entry->value) : NULL;
		}
	} else {
		if (exists) {
			*exists = 0;
		}
		return NULL;
	}
}

[rjhdby]

In this case - any value that not in the ini-storage.
If somename exists in storage then this function returns it's value otherwise returns null

[rjhdby]

Thank Mike, I'll go try.

[msink]

So it dont have to be stable pointer, your original code should work, if just replace sizeof to strlen.

[rjhdby]

Yes, it must work with strlen, but it's external library function and I can't change definition of macro 😞

[svyatoslav.scherbina]

This macro looks pretty simple. Isn’t it possible to write proper Kotlin function instead?

[rjhdby]

Svyatoslav, this macro used for backward compatibility. No guarantee that this macro keeps unchanged in future.

[svyatoslav.scherbina]

Yes. But its current implementation is supposed to remain valid in future, otherwise this library would not have binary compatibility when used from C.

[Andrey Gromov]

It's rare case. 🙂
I writing "framework" for PHP-extension development with KN. It must be compatible with various version of zend api. But almost all zend api's functions have recomended access through macro.

[olonho]

Why cannot you append all compile-time known strings to the .def file and use C macros from there?

[rjhdby]

Uhhh... It is not private one-time project. I make something like proxy between KN and zend libraries. Main purpose (excluding education) is create tools for php-extension development with KN. All user space php-functions will be described by dsl and connected to KN functions, where defined those compile-time strings.
User manual with instructions like "define all used string constants in separated .def file" smell a little.
Other way is parse .kt sources and autogenerate .def, but...

[olonho]

So, the I assume solution suggested by Mike with explicit strlen() would be the best one