From 0a95c7bd7268c4c97dffec64fa6e08d12cb37a40 Mon Sep 17 00:00:00 2001
From: Walter Karas <wkaras@verizonmedia.com>
Date: Wed, 9 Feb 2022 20:19:29 -0600
Subject: [PATCH] Send diags output to stderr when running regression tests.

---
 include/tscore/Regression.h          |  2 ++
 src/traffic_server/traffic_server.cc |  3 +++
 src/tscore/Diags.cc                  | 12 ++++++++++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/tscore/Regression.h b/include/tscore/Regression.h
index 72e65fa2c4b..6c58973817a 100644
--- a/include/tscore/Regression.h
+++ b/include/tscore/Regression.h
@@ -101,3 +101,5 @@ struct RegressionTest {
 int rprintf(RegressionTest *t, const char *format, ...);
 int rperf(RegressionTest *t, const char *tag, double val);
 const char *regression_status_string(int status);
+
+void tell_diags_regression_testing_is_on();
diff --git a/src/traffic_server/traffic_server.cc b/src/traffic_server/traffic_server.cc
index c9520300f7d..f5f169ac3cd 100644
--- a/src/traffic_server/traffic_server.cc
+++ b/src/traffic_server/traffic_server.cc
@@ -1570,6 +1570,9 @@ static void
 run_RegressionTest()
 {
   if (regression_level) {
+    // Call this so that Diags.cc will send diagnostic output to stderr.
+    tell_diags_regression_testing_is_on();
+
     eventProcessor.schedule_every(new RegressionCont(), HRTIME_SECONDS(1));
   }
 }
diff --git a/src/tscore/Diags.cc b/src/tscore/Diags.cc
index 20d22ec7a5f..ef0ac93da19 100644
--- a/src/tscore/Diags.cc
+++ b/src/tscore/Diags.cc
@@ -44,7 +44,7 @@
 #include "tscore/ink_time.h"
 #include "tscore/ink_hrtime.h"
 #include "tscore/ink_thread.h"
-#include "tscore/BufferWriter.h"
+#include "tscore/Regression.h"
 #include "tscore/Diags.h"
 
 int diags_on_for_plugins         = 0;
@@ -53,6 +53,14 @@ int DiagsConfigState::enabled[2] = {0, 0};
 // Global, used for all diagnostics
 Diags *diags = nullptr;
 
+static bool regression_testing_on = false;
+
+void
+tell_diags_regression_testing_is_on()
+{
+  regression_testing_on = true;
+}
+
 static bool
 location(const SourceLocation *loc, DiagsShowLocation show, DiagsLevel level)
 {
@@ -266,7 +274,7 @@ Diags::print_va(const char *debug_tag, DiagsLevel diags_level, const SourceLocat
     }
   }
 
-  if (config.outputs[diags_level].to_stderr) {
+  if (config.outputs[diags_level].to_stderr || regression_testing_on) {
     if (stderr_log && stderr_log->m_fp) {
       va_list tmp;
       va_copy(tmp, ap);