Mysterious (to me) Xdebug issue with PHP 7.3 View as Markdown

Hi Derick,

The message "Invalid opcode 17/1/8" means that PHP doesn't have handler for opcode 17 (ZEND_IS_EQUAL) where first operand IS_CONST and second operand IS_CV.

ZEND_IS_EQUAL is a commutative operator. zend_vm_gen.php doesn't generate code for ZEND_IS_EQUAL_SPEC_CONST_CV_HANDLER, but PHP code-generator swaps operands, if necessary, to use ZEND_IS_EQUAL_SPEC_CV_CONST_HANDLER.

ZEND_API void ZEND_FASTCALL zend_vm_set_opcode_handler(zend_op* op)
{
zend_uchar opcode = zend_user_opcodes[op->opcode];
uint32_t spec = zend_spec_handlers[opcode];

if (spec & SPEC_RULE_COMMUTATIVE) {
    if (op->op1_type < op->op2_type) {
        zend_swap_operands(op);
    }
}
op->handler = zend_vm_get_opcode_handler_ex(spec, op);

}

I have no idea, why PHP with xdebug doen't swap operands.

Thanks. Dmitry.

Hi Dmitry,

this indeed seems to fix the problem — thanks!

cheers,
Derick

I hope, it's fixed now.

Please verify.

Dmitry.

---

From: Dmitry Stogov dmitry@zend.com
Sent: Wednesday, September 5, 2018 1:36:33 PM
To: Derick Rethans
Cc: PHP Developers Mailing List
Subject: Re: [PHP-DEV] Re: Mysterious (to me) Xdebug issue with PHP 7.3

I see the problem, and most probably, it has to be fixed in PHP sources.

I'll try to take a deeper look today evening.

Thanks. Dmitry.

---

From: Derick Rethans derick@php.net
Sent: Wednesday, September 5, 2018 12:27:56 PM
To: Dmitry Stogov
Cc: PHP Developers Mailing List
Subject: [PHP-DEV] Re: Mysterious (to me) Xdebug issue with PHP 7.3

Hi,

in Xdebug, I do supply my own opcode handlers for quite a few opcodes,
including ZEND_IS_EQUAL, and a whole bunch of others. Is it possible
that when you use zend_set_user_opcode_handler[1][2] that this swap
isn't done with zend_swap_operands? My opcode handler basically just
does some code and then uses ZEND_VM_DISPATCH[3].

[1] https://github.com/derickr/xdebug/blob/PHP-7.3-support/xdebug_code_coverage.h#L47-L48
[2] https://github.com/derickr/xdebug/blob/PHP-7.3-support/xdebug.c#L781
[3] https://github.com/derickr/xdebug/blob/PHP-7.3-support/xdebug_code_coverage.c#L125-L142

cheers,
Derick

Hi Derick,

The message "Invalid opcode 17/1/8" means that PHP doesn't have handler for opcode 17 (ZEND_IS_EQUAL) where first operand IS_CONST and second operand IS_CV.

ZEND_IS_EQUAL is a commutative operator. zend_vm_gen.php doesn't generate code for ZEND_IS_EQUAL_SPEC_CONST_CV_HANDLER, but PHP code-generator swaps operands, if necessary, to use ZEND_IS_EQUAL_SPEC_CV_CONST_HANDLER.

ZEND_API void ZEND_FASTCALL zend_vm_set_opcode_handler(zend_op* op)
{
zend_uchar opcode = zend_user_opcodes[op->opcode];
uint32_t spec = zend_spec_handlers[opcode];

if (spec & SPEC_RULE_COMMUTATIVE) {
    if (op->op1_type < op->op2_type) {
        zend_swap_operands(op);
    }
}
op->handler = zend_vm_get_opcode_handler_ex(spec, op);

}

I have no idea, why PHP with xdebug doen't swap operands.

Thanks. Dmitry.

---

From: Derick Rethans derick@php.net
Sent: Tuesday, September 4, 2018 7:26:49 PM
To: Dmitry Stogov
Cc: PHP Developers Mailing List
Subject: Mysterious (to me) Xdebug issue with PHP 7.3

Hi,

I'm finalizing Xdebug support for PHP 7.3, and although I have fixed
many things, there is one thing that is (currently) eluding me.

The branch I'm working on is
https://github.com/derickr/xdebug/tree/PHP-7.3-support

With Xdebug (just) loaded, the following script:

    $ cat /tmp/bug01471.php
    <?php
    $c = "aa" == $ff ? 1 : 0;
    ?>

Fails to run with:

    $ php -n -dzend_extension=xdebug.so /tmp/bug01471.php

    Fatal error: Invalid opcode 17/1/8. in /tmp/bug01471.php on line 2

    Call Stack:
        0.0002          0   1. {main}() /tmp/bug01471.php:0

I also see others, like when running with a Composer library:

    $ vendor/bin/phpunit --debug

    Fatal error: Invalid opcode 16/1/2. in /home/derick/dev/php/derickr-mongo-php-library/vendor/composer/autoload_real.php on line 18

    Call Stack:
        0.0003     431424   1. {main}() /home/derick/dev/php/derickr-mongo-php-library/vendor/phpunit/phpunit/phpunit:0
        0.0005     433616   2. require('/home/derick/dev/php/derickr-mongo-php-library/vendor/autoload.php') /home/derick/dev/php/derickr-mongo-php-library/vendor/phpunit/phpunit/phpunit:51
        0.0008     450432   3. ComposerAutoloaderInit96731179a4aab6838b54de3a71995ee1::getLoader() /home/derick/dev/php/derickr-mongo-php-library/vendor/autoload.php:7

And I can't figure out why. The backtrace isn't particularly useful
either. I got similar issues with get_zval_ptr [1], as it changed, but I
can't track this specific one down. Would you mind having a look?

cheers,
Derick

[1] https://github.com/derickr/xdebug/commit/70d9189700d57707d842020493a3df23e0c76098

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--
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Like Xdebug? Consider a donation: https://xdebug.org/donate.php,
or become my Patron: https://www.patreon.com/derickr
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--
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Like Xdebug? Consider a donation: https://xdebug.org/donate.php,
or become my Patron: https://www.patreon.com/derickr
twitter: @derickr and @xdebug