Hi!
I am working on making Xdebug work properly with PHP 7.3, and over the
last week I have been tearing my hair out as to why Xdebug's view of
opcodes was no longer showing the opcodes that OPcache had
modified/optimised. In PHP 7.2, the order in which you load Xdebug and
OPcache made a difference.
OPcache optimises out line 6, which has dead code:
1 <?php
2
3 try
4 {
5 throw new Exception();
6 echo strlen( "Revenge is a dish best served cold.\n" );
7 }
8 catch(Exception $e)
9 {
10 }
11
12 echo strlen( "The fire is always hotter on someone elses face." ), "\n";
13 ?>
derick@singlemalt:~/dev/php/derickr-xdebug $ /usr/local/php/7.2.13/bin/php -n
-dzend_extension=opcache.so -d "zend_extension=xdebug.so" -d
"opcache.enable=1" -d "opcache.enable_cli=1" -d "xdebug.extended_info=1"
-dvld.active=1 -f
"/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php"
48
/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php:7:
array(4) {
[5] =>
int(1)
[8] =>
int(1)
[12] =>
int(1)
[14] =>
int(1)
}
[GIT: issue1598-no-code-coverage-with-opcache][PHP: 7.2.13 ]
derick@singlemalt:~/dev/php/derickr-xdebug $ /usr/local/php/7.2.13/bin/php -n
-d "zend_extension=xdebug.so" -dzend_extension=opcache.so -d "opcache.enable=1"
-d "opcache.enable_cli=1" -d "xdebug.extended_info=1" -dvld.active=1 -f
"/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php"
48
/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php:7:
array(5) {
[5] =>
int(1)
[6] =>
int(-2)
[8] =>
int(1)
[12] =>
int(1)
[14] =>
int(1)
}
Where as with PHP 7.3.0, they both show the *unoptimised* version:
derick@singlemalt:~/dev/php/derickr-xdebug $ /usr/local/php/7.3.0/bin/php -n
-dzend_extension=opcache.so -d "zend_extension=xdebug.so" -d
"opcache.enable=1" -d "opcache.enable_cli=1" -d "xdebug.extended_info=1"
-dvld.active=1 -f
"/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php"
48
/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php:7:
array(5) {
[5] =>
int(1)
[6] =>
int(-2)
[8] =>
int(1)
[12] =>
int(1)
[14] =>
int(1)
}
[GIT: issue1598-no-code-coverage-with-opcache][PHP: 7.2.13 ]
derick@singlemalt:~/dev/php/derickr-xdebug $ /usr/local/php/7.3.0/bin/php -n
-d "zend_extension=xdebug.so" -dzend_extension=opcache.so -d "opcache.enable=1"
-d "opcache.enable_cli=1" -d "xdebug.extended_info=1" -dvld.active=1 -f
"/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php"
48
/home/derick/dev/php/derickr-xdebug/tests/bug00213-php73-opcache.php:7:
array(5) {
[5] =>
int(1)
[6] =>
int(-2)
[8] =>
int(1)
[12] =>
int(1)
[14] =>
int(1)
}
Curiously, vld, would always show the right (optimised) opcodes:
filename: /home/derick/dev/php/derickr-xdebug/tests/bug00213.inc
function name: (null)
number of ops: 12
compiled vars: !0 = $e
line #* E I O op fetch ext return
operands
-------------------------------------------------------------------------------------
5 0 E > EXT_STMT
1 NEW $1 :-5
2 EXT_FCALL_BEGIN
3 DO_FCALL 0
4 EXT_FCALL_END
5 > THROW 0 $1
8 6 E > > CATCH
'Exception', !0
12 7 > EXT_STMT
8 ECHO 48
9 EXT_STMT
10 ECHO '%0A'
14 11 > RETURN 1
branch: # 0; line: 5- 5; sop: 0; eop: 5; out0: -2
branch: # 6; line: 8- 8; sop: 6; eop: 6; out0: 7; out1: -2
branch: # 7; line: 12- 14; sop: 7; eop: 11; out0: -2
path #1: 0,
path #2: 6, 7,
So I did some digging and found out that OPcache in PHP 7.3 has had a change
to the loading order. This was done in:
https://github.com/php/php-src/commit/b4903aef16ec215f2095ff0a3615524656401660:
commit b4903aef16ec215f2095ff0a3615524656401660
Author: Dmitry Stogov <[email protected]>
Date: Wed Oct 18 17:18:54 2017 +0300
Move a part of opcache initialization into post_startup phase
(when all extensions already loaded).
Both Xdebug and OPcache hook into zend_compile. In PHP 7.2, when as per
documentation, OPcache was loaded after Xdebug, OPcache's zend_compile
(accel_startup) was run *first*, so that Xdebug sees the optimised
opcodes.
In PHP 7.3, after the above commit, Xdebug's zend_compile hook
(xdebug_compile_file) is run before OPcache's — *no matter which
extension is loaded first*. Due to this, Xdebug can not properly do code
coverage anymore when OPcache is also present, as it can only see
*unoptimised* oparrays during its zend_compile hook.
Because opcodes may now differ between when Xdebug analyses oparrays
(zend_compile stage) and when it uses it (zend_execute stage) the
results can be inconsistent in OPcache has optimised things away, and/or
rearranged branches.
Right now, I don't think I have a choice but to disallow code coverage
analysis when OPcache is present, but I would prefer finding a solution
to this so that OPcache and Xdebug work together again, as it did for
PHP versions before 7.3.
cheers,
Derick
--
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