Fixing Segfault/garbage data for attributes (#93)

* Add failing test for incorrect gc count for attributes

* Fix the GC count for the returned attributes array.

When returning our internal HashTable as a zval to user-space, we need
to increment the GC count. If the user-space variable is destroyed, then
our HashTable with our attributes could be destroyed. References to
these values could work, could segfault, or could have garbage data.

Author: chingor13

ext/opencensus_trace_span.c

@@ -533,7 +533,7 @@ int opencensus_trace_span_to_zval(opencensus_trace_span_t *trace_span, zval *spa
     zend_update_property_double(opencensus_trace_span_ce, span, "endTime", sizeof("endTime") - 1, trace_span->stop);
 
     array_init(&attributes);
-    zend_hash_copy(Z_ARRVAL(attributes), trace_span->attributes, NULL);
+    zend_hash_copy(Z_ARRVAL(attributes), trace_span->attributes, zval_add_ref);
     zend_update_property(opencensus_trace_span_ce, span, "attributes", sizeof("attributes") - 1, &attributes);
 
     zend_update_property(opencensus_trace_span_ce, span, "stackTrace", sizeof("stackTrace") - 1, &trace_span->stackTrace);

ext/tests/bug_001.phpt

@@ -0,0 +1,49 @@
+--TEST--
+OpenCensus Trace: Bug 001: Attributes incorrect GC count yields garbage data.
+--FILE--
+<?php
+
+function myEcho ($var) {
+    echo $var . PHP_EOL;
+}
+
+function execute() {
+    $str = "Hello World!";
+    myEcho($str);
+}
+
+function allocate_strings($count) {
+    $foo = "asdf";
+    for ($i = 0; $i < $count; $i++) {
+        $foo .= ",$i";
+    }
+}
+
+function inspect() {
+    $span = opencensus_trace_list()[0];
+    print_r($span->attributes());
+}
+
+// 1: Sanity test a simple profile run
+opencensus_trace_function("myEcho", function ($x) {
+    return ['name' => 'foo', 'startTime' => 0.1, 'attributes' => ['text' => $x]];
+});
+
+execute();
+execute();
+
+inspect();
+inspect();
+
+?>
+--EXPECT--
+Hello World!
+Hello World!
+Array
+(
+    [text] => Hello World!
+)
+Array
+(
+    [text] => Hello World!
+)