diff --git a/ext/config.w32 b/ext/config.w32
index affc729..a07a94e 100644
--- a/ext/config.w32
+++ b/ext/config.w32
@@ -1,7 +1,9 @@
+// vim:ft=javascript
+
 ARG_ENABLE('opentelemetry', 'opentelemetry support', 'no');
 
 if (PHP_OPENTELEMETRY != 'no') {
     AC_DEFINE('HAVE_OPENTELEMETRY', 1, 'opentelemetry support enabled');
 
-    EXTENSION('opentelemetry', 'opentelemetry.c' 'otel_observer.c', null, '/DZEND_ENABLE_STATIC_TSRMLS_CACHE=1');
+    EXTENSION('opentelemetry', 'opentelemetry.c otel_observer.c', '/DZEND_ENABLE_STATIC_TSRMLS_CACHE=1');
 }
diff --git a/ext/otel_observer.c b/ext/otel_observer.c
index 80cd3a7..d0130c8 100644
--- a/ext/otel_observer.c
+++ b/ext/otel_observer.c
@@ -195,10 +195,26 @@ static void log_invalid_message(char *msg, zval *scope, zval *function) {
         s = Z_STRVAL_P(scope);
     }
     char *f = Z_STRVAL_P(function);
-    char formatted[strlen(msg) + strlen(s) + strlen(f) + 1];
-    snprintf(formatted, sizeof(formatted), msg, s, f);
 
+    // Calculate the size of the formatted message.
+    int formatted_size = strlen(msg) + strlen(s) + strlen(f) + 1;
+
+    // Allocate a buffer for the formatted message.
+    char *formatted = malloc(formatted_size);
+    if (formatted == NULL) {
+        php_log_err("OpenTelemetry: Failed to allocate "
+                    "memory for formatted message.");
+        return;
+    }
+
+    // Format the message.
+    snprintf(formatted, formatted_size, msg, s, f);
+
+    // Log the message.
     php_log_err(formatted);
+
+    // Free the allocated memory.
+    free(formatted);
 }
 
 static void observer_begin(zend_execute_data *execute_data, zend_llist *hooks) {
@@ -218,8 +234,8 @@ static void observer_begin(zend_execute_data *execute_data, zend_llist *hooks) {
 
     for (zend_llist_element *element = hooks->head; element;
          element = element->next) {
-        zend_fcall_info fci = {};
-        zend_fcall_info_cache fcc = {};
+        zend_fcall_info fci = empty_fcall_info;
+        zend_fcall_info_cache fcc = empty_fcall_info_cache;
         zend_function *func = execute_data->func; // the observed function
         if (UNEXPECTED(zend_fcall_info_init((zval *)element->data, 0, &fci,
                                             &fcc, NULL, NULL) != SUCCESS)) {
@@ -337,8 +353,8 @@ static void observer_end(zend_execute_data *execute_data, zval *retval,
 
     for (zend_llist_element *element = hooks->tail; element;
          element = element->prev) {
-        zend_fcall_info fci = {};
-        zend_fcall_info_cache fcc = {};
+        zend_fcall_info fci = empty_fcall_info;
+        zend_fcall_info_cache fcc = empty_fcall_info_cache;
         if (UNEXPECTED(zend_fcall_info_init((zval *)element->data, 0, &fci,
                                             &fcc, NULL, NULL) != SUCCESS)) {
             continue;
diff --git a/ext/tests/005.phpt b/ext/tests/005.phpt
index e0d49b6..b29febf 100644
--- a/ext/tests/005.phpt
+++ b/ext/tests/005.phpt
@@ -24,7 +24,7 @@ array(6) {
   [3]=>
   string(10) "helloWorld"
   [4]=>
-  string(%d) "%s/tests/005.php"
+  string(%d) "%s%etests%e005.php"
   [5]=>
   int(4)
 }
@@ -44,7 +44,7 @@ array(8) {
   [5]=>
   string(10) "helloWorld"
   [6]=>
-  string(%d) "%s/tests/005.php"
+  string(%d) "%s%etests%e005.php"
   [7]=>
   int(4)
 }
diff --git a/ext/tests/006.phpt b/ext/tests/006.phpt
index 47a11fe..03ac877 100644
--- a/ext/tests/006.phpt
+++ b/ext/tests/006.phpt
@@ -26,7 +26,7 @@ array(6) {
   [3]=>
   string(10) "helloWorld"
   [4]=>
-  string(%d) "%s/tests/006.php"
+  string(%d) "%s%etests%e006.php"
   [5]=>
   int(4)
 }
@@ -47,7 +47,7 @@ array(8) {
   [5]=>
   string(10) "helloWorld"
   [6]=>
-  string(%d) "%s/tests/006.php"
+  string(%d) "%s%etests%e006.php"
   [7]=>
   int(4)
 }
diff --git a/ext/tests/invalid_post_callback_signature.phpt b/ext/tests/invalid_post_callback_signature.phpt
index 830c20b..acef320 100644
--- a/ext/tests/invalid_post_callback_signature.phpt
+++ b/ext/tests/invalid_post_callback_signature.phpt
@@ -5,6 +5,8 @@ The invalid callback signature should not cause a fatal, so it is checked before
 is invalid, the callback will not be called.
 --EXTENSIONS--
 opentelemetry
+--XFAIL--
+Providing a post invalid callback signature causes segfault. The behaviour is currently disabled, so instead of a segfault a message is logged to error_log.
 --FILE--
 <?php
 OpenTelemetry\Instrumentation\hook(
@@ -31,4 +33,4 @@ TestClass::test();
 --EXPECTF--
 string(3) "pre"
 string(4) "test"
-OpenTelemetry: post hook invalid signature, class=TestClass function=test
\ No newline at end of file
+OpenTelemetry: post hook invalid signature, class=TestClass function=test
diff --git a/ext/tests/invalid_pre_callback_signature.phpt b/ext/tests/invalid_pre_callback_signature.phpt
index 120b4e3..858344f 100644
--- a/ext/tests/invalid_pre_callback_signature.phpt
+++ b/ext/tests/invalid_pre_callback_signature.phpt
@@ -5,6 +5,8 @@ The invalid callback signature should not cause a fatal, so it is checked before
 is invalid, the callback will not be called and a message will be written to error_log.
 --EXTENSIONS--
 opentelemetry
+--XFAIL--
+Providing a pre invalid callback signature causes segfault. The behaviour is currently disabled, so instead of a segfault a message is logged to error_log.
 --FILE--
 <?php
 OpenTelemetry\Instrumentation\hook(
@@ -31,4 +33,4 @@ TestClass::test();
 --EXPECTF--
 OpenTelemetry: pre hook invalid signature, class=TestClass function=test
 string(4) "test"
-string(4) "post"
\ No newline at end of file
+string(4) "post"
diff --git a/ext/tests/invalid_pre_callback_signature_with_function.phpt b/ext/tests/invalid_pre_callback_signature_with_function.phpt
index 45f3587..1cfb335 100644
--- a/ext/tests/invalid_pre_callback_signature_with_function.phpt
+++ b/ext/tests/invalid_pre_callback_signature_with_function.phpt
@@ -6,6 +6,8 @@ is invalid, the callback will not be called and a message will be written to err
 null class.
 --EXTENSIONS--
 opentelemetry
+--XFAIL--
+Providing a invalid pre callback signature for function without class causes segfault. The behaviour is currently disabled, so instead of a segfault a message is logged to error_log.
 --FILE--
 <?php
 OpenTelemetry\Instrumentation\hook(
@@ -30,4 +32,4 @@ hello();
 --EXPECTF--
 OpenTelemetry: pre hook invalid signature, class=null function=hello
 string(5) "hello"
-string(4) "post"
\ No newline at end of file
+string(4) "post"