Mem leak in PHP 7.1.* with DYNAMIC_MALLOC_SPRINTF when type IS_OBJECT

[asgrim]

For some reason, there's a memory leak in PHP 7.1.* with the DYNAMIC_MALLOC_SPRINTF macro used in the IS_OBJECT branch of safely_copy_argument_zval_as_scalar. I tried a few things but couldn't get to the bottom of it. As a workaround, for PHP 7.1.* I just return the string (object) rather than the actual object type, but it would be nice if we could get to the bottom of this.

Note: whilst tests only show failures after PHP 7.1.17+ this is because 7.1.16 and below did not have REPORT_EXIT_STATUS=1 as default.

[asgrim]

Note, the $client->getRange('foo', 0, 2); causes it to fail in the Predis test, because the argument is an object, so that's a good testcase. Script to reproduce in example.php:

<?php

require "/tmp/scout_predis_test/vendor/autoload.php";

$client = new \Predis\Client();

$client->set('foo', 'bar');
echo $client->getRange('foo', 0, 2);

var_dump(scoutapm_get_calls());

Command to memcheck:

ZEND_DONT_UNLOAD_MODULES=1 USE_ZEND_ALLOC=0 valgrind --leak-check=full /home/james/workspace/php-src-build/bin/php -d zend_extension=`pwd`/modules/scoutapm.so example.php

Or the test suite as a whole:

/home/james/workspace/php-src-build/bin/php run-tests.php -p /home/james/workspace/php-src-build/bin/php -d zend_extension=`pwd`/modules/scoutapm.so -g "FAIL,XFAIL,BORK,WARN,LEAK,SKIP" --offline --show-diff --set-timeout 120 -m -q