From 0e89f68662647f0808d3ff9d23a53a9829d1652d Mon Sep 17 00:00:00 2001
From: Giulio Eulisse <10544+ktf@users.noreply.github.com>
Date: Thu, 20 Nov 2025 13:23:33 +0100
Subject: [PATCH] DPL: fix thread safety of slot allocation in runtime_error_f

---
 Framework/Foundation/src/RuntimeError.cxx | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/Framework/Foundation/src/RuntimeError.cxx b/Framework/Foundation/src/RuntimeError.cxx
index 6f31fb40b86f5..7d31389a9641c 100644
--- a/Framework/Foundation/src/RuntimeError.cxx
+++ b/Framework/Foundation/src/RuntimeError.cxx
@@ -60,8 +60,11 @@ RuntimeError& error_from_ref(RuntimeErrorRef ref)
 RuntimeErrorRef runtime_error_f(const char* format, ...)
 {
   int i = 0;
-  bool expected = false;
-  while (gErrorBooking[i].compare_exchange_strong(expected, true) == false) {
+  while (true) {
+    bool expected = false;
+    if (gErrorBooking[i].compare_exchange_strong(expected, true) == true) {
+      break;
+    }
     ++i;
     if (i >= RuntimeError::MAX_RUNTIME_ERRORS) {
       throw std::runtime_error("Too many o2::framework::runtime_error thrown without proper cleanup.");
@@ -78,11 +81,18 @@ RuntimeErrorRef runtime_error_f(const char* format, ...)
 RuntimeErrorRef runtime_error(const char* s)
 {
   int i = 0;
-  bool expected = false;
-  while (gErrorBooking[i].compare_exchange_strong(expected, true) == false) {
+  while (true) {
+    bool expected = false;
+    if (gErrorBooking[i].compare_exchange_strong(expected, true) == true) {
+      break;
+    }
     ++i;
+    if (i >= RuntimeError::MAX_RUNTIME_ERRORS) {
+      throw std::runtime_error("Too many o2::framework::runtime_error thrown without proper cleanup.");
+    }
   }
-  strncpy(gError[i].what, s, RuntimeError::MAX_RUNTIME_ERROR_SIZE);
+  strncpy(gError[i].what, s, RuntimeError::MAX_RUNTIME_ERROR_SIZE - 1);
+  gError[i].what[RuntimeError::MAX_RUNTIME_ERROR_SIZE - 1] = 0;
   gError[i].maxBacktrace = canDumpBacktrace() ? backtrace(gError[i].backtrace, BacktraceHelpers::MAX_BACKTRACE_SIZE) : 0;
   return RuntimeErrorRef{i};
 }