Add tests/oom_dump.phpt for the memory_limit auto-dump

package.xml

@@ -46,6 +46,7 @@ Initial release.
     <file name="dump.phpt" role="test"/>
     <file name="file_perms.phpt" role="test"/>
     <file name="full_flag.phpt" role="test"/>
+    <file name="oom_dump.phpt" role="test"/>
     <file name="overwrite_inode.phpt" role="test"/>
     <file name="safe_read.phpt" role="test"/>
     <file name="set_oom_dump.phpt" role="test"/>

tests/oom_dump.phpt

@@ -0,0 +1,57 @@
+--TEST--
+rdump.oom_dump writes a well-formed RDUMP dump when memory_limit is exhausted
+--SKIPIF--
+<?php
+if (!extension_loaded("rdump")) die("skip rdump not loaded");
+if (PHP_OS_FAMILY !== "Linux") die("skip Linux only");
+if (!is_file(dirname(__DIR__) . "/modules/rdump.so")) die("skip built modules/rdump.so not found");
+if (!function_exists("shell_exec") || !shell_exec("echo ok")) die("skip shell_exec disabled");
+?>
+--FILE--
+<?php
+// A memory_limit error is fatal, so it can only be observed from a separate
+// process: spawn a child that exhausts memory with rdump.oom_dump set, then
+// verify from here that the extension auto-dumped at the moment of death.
+$so   = dirname(__DIR__) . "/modules/rdump.so";
+$php  = getenv("TEST_PHP_EXECUTABLE");
+if ($php === false || $php === "") {
+    $php = PHP_BINARY;
+}
+
+$dump  = sys_get_temp_dir() . "/rdump_oom_" . getmypid() . ".rdump";
+$child = sys_get_temp_dir() . "/rdump_oom_child_" . getmypid() . ".php";
+@unlink($dump);
+@unlink($dump . ".done");
+file_put_contents($child, '<?php $a = []; while (true) { $a[] = str_repeat("x", 4096); }');
+
+$cmd = escapeshellarg($php)
+     . " -n"
+     . " -d extension=" . escapeshellarg($so)
+     . " -d memory_limit=16M"
+     . " -d rdump.oom_dump=" . escapeshellarg($dump)
+     . " -d rdump.oom_dump_marker=1"
+     . " " . escapeshellarg($child)
+     . " 2>&1";
+$output = (string) shell_exec($cmd);
+
+// The child died on the memory_limit error...
+var_dump(strpos($output, "Allowed memory size") !== false);
+
+// ...and the OOM hook wrote the dump without any rdump_dump() call.
+var_dump(is_file($dump));
+
+// The dump is a well-formed RDUMP file.
+var_dump(file_get_contents($dump, false, null, 0, 8) === "RDUMP\0\0\0");
+
+// The completion marker was written (rdump.oom_dump_marker=1).
+var_dump(is_file($dump . ".done"));
+
+@unlink($dump);
+@unlink($dump . ".done");
+@unlink($child);
+?>
+--EXPECT--
+bool(true)
+bool(true)
+bool(true)
+bool(true)