Re: FFI extension / NULL-Checks

In response to these findings so far, I have now submitted https://github.com/php/php-src/pull/4691 that adds an FFI::isNull() method that returns true if the passed CData instance points to NULL. If you agree that something like this is indeed needed, I will gladly update the PR and add unit tests. Philip On Mon, Sep 9, 2019 at 8:03 AM Philip Hofstetter <phofstetter@sensational.ch> wrote: > Hello, > > (I'm writing to the internals list because I don't think that at this > point, FFI usage is wide-spread enough to get an opinion on other venues) > > maybe I'm just stupid, but I think there has been a slight oversight in > the API design for the FFI interface. > > My problem is with functions that return a pointer to a struct as an out > parameter. > > So in C, it would look like this: > > Error* err; > func(&err); > > if (err != NULL){ > do_error_handling(); > } > > If I translate this to PHP FFI, I would do > > $err = $ffi->new("Error*"); > $ffi->func(FFI::addr($err)); > > if I var_dump $err, I do see a public {0} property be set to > NULL or to > actual error data. > > My issue is though: How do I check whether err* as been assgined to? > > isset($err) > $err[0] != null > -> is always true, regardless of whether func as assigned an error or not > > isset($err->{0}) > isset($err[0]) > -> Cannot use object of type FFI\CData as array > > $err->{0} != NULL; > -> FFI\Exception: NULL pointer dereference > > $err[0]; > -> segfault > > I'm sure I must be doing something wrong, but I don't know what. Also, the > documentation could do with an example on how to achieve the desired result > and, TBH, I think some of the various attempts produce a somewhat > unexpected output. > > Any comments? > > Philip > > > var_dump(isset($r->{0})); > -> Error: Cannot use object of type FFI\CData as array > > $a = '{0}'; > var_dump(isset($r->$a)); > -> Error: Cannot use object of type FFI\CData as array > > > var_dump(isset($r[0])); > var_dump($r[0]); > > > -- Sensational AG Giesshübelstrasse 62c, Postfach 1966, 8021 Zürich Tel. +41 43 544 09 60, Mobile +41 79 341 01 99 info@sensational.ch, http://www.sensational.ch