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Date: Tue, 13 Mar 2018 08:52:56 +0100
To: Sara Golemon <pollita@php.net>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Migrating php extension from 5 to 7, ZVAL_STRINGL no
 value returned
From: richard@klingler.net (Richard Klingler)

Hello Sara

Seems my post to news.php.net went somehow through though my NNTP client complained about errors...anyway (o;

"mycount" is defined in here:

     FUN_ACCESSOR(mycount)

Which is the updated by the read function.

The function macro itself is defined as:

	ZEND_FE(readmydevice,		NULL)

So would the arg_info go in here? There isn't any arg_info in the original code.


thanks in advance
richard


On Mon, 12 Mar 2018 13:18:30 -0400, Sara Golemon wrote:
> On Mon, Mar 12, 2018 at 12:16 PM, Richard Klingler 
> <richard@klingler.net> wrote:
>> ZEND_FUNCTION(readmydevice)
>> {
>>         zend_long n;
>>         zval *z;
>>         size_t len;
>>         char *p;
>>         long r;
>> 
>>         if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "lzl", &n,
>> &z, &len) == FAILURE) {
>>                 return;
>>         }
>> 
>>         p = (char *) emalloc(len + 1);
>>         memset(p,0,len+1);
>> 
>>         r = myread(n, p, len);
>>         printf("Read %d bytes from device %d up to %d bytes\n", mycount,
>> n, len);
>>         p[ibcnt] = '\0';
>>         ZVAL_STRINGL(z, p, mycount);
>>         printf("Returned %s\n", p);
>>         efree(p);
>>         RETURN_LONG(r);
>> }
>> 
>> 
>> Any ideas why ZVAL_STRINGL is not doing anything?
>> Or did I miss something?
>> 
> Well, ZVAL_STRINGL is probably doing something, but there are two
> reasons there's no way to be certain:
> 
> 1. What is 'mycount' and where does it come from / how is it set?  If
> it's zero, then you'll be saving a zero length string. In any case, it
> doesn't seem to have any relationship to the data read into `p`.  I'm
> guessing you wanted to use `r` rather than `mycount` both here and in
> your debug message.
> 
> 2. I'm inferring that you want argument 2 to your function to be a
> pass-by-ref argument.  Are you specifying any arg_info in the function
> entry list? (where you have your PHP_FE macro -- or perhaps ZEND_FE
> macro, since you seem to be using those versions).  In order to pass
> by ref, you need that structure to specify that the argument is
> by-ref.  This *might* have worked without it in PHP 5, but only by
> accident and would have probably failed in hard-to-diagnose ways.
> 
> 2a. Also, when using by-ref args, you need to destruct any previously
> held value.  In this case, with a zval_dtor(z); prior to the
> ZVAL_STRINGL() macro.
> 
> -Sara