From b20419efaf58ae6da2aed9f115961bfcefda40a9 Mon Sep 17 00:00:00 2001
From: Tim Wojtulewicz <tim@corelight.com>
Date: Thu, 17 Apr 2025 13:23:37 -0700
Subject: [PATCH] Fix clang-tidy bugprone-suspicious-realloc-usage warnings

---
 .clang-tidy     |  1 +
 src/Reporter.cc | 51 +++++++++++++++++++++++++++++++------------------
 2 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/.clang-tidy b/.clang-tidy
index 3b8a2139c1..d7ebf7a090 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -13,4 +13,5 @@ Checks: [-*,
          bugprone-suspicious-stringview-data-usage,
          bugprone-suspicious-string-compare,
          bugprone-suspicious-include,
+         bugprone-suspicious-realloc-usage,
 ]
diff --git a/src/Reporter.cc b/src/Reporter.cc
index 217fd277b2..43510b315f 100644
--- a/src/Reporter.cc
+++ b/src/Reporter.cc
@@ -475,7 +475,8 @@ void Reporter::Deprecation(std::string_view msg, const detail::Location* loc1, c
 
 void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Connection* conn, ValPList* addl,
                      bool location, bool time, const char* postfix, const char* fmt, va_list ap) {
-    static char tmp[512];
+    constexpr size_t DEFAULT_BUFFER_SIZE = 512;
+    static char tmp[DEFAULT_BUFFER_SIZE];
 
     int size = sizeof(tmp);
     char* buffer = tmp;
@@ -522,27 +523,38 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Conne
         }
     }
 
-    while ( true ) {
-        va_list aq;
-        va_copy(aq, ap);
-        int n = vsnprintf(buffer, size, fmt, aq);
-        va_end(aq);
+    // Figure out how big of a buffer is needed here.
+    va_list ap_copy;
+    va_copy(ap_copy, ap);
+    size_t req_buffer_size = vsnprintf(nullptr, 0, fmt, ap_copy);
 
-        if ( postfix )
-            n += strlen(postfix) + 10; // Add a bit of slack.
-
-        if ( n > -1 && n < size )
-            // We had enough space;
-            break;
-
-        // Enlarge buffer;
-        size *= 2;
-        buffer = allocated = (char*)realloc(allocated, size);
-
-        if ( ! buffer )
-            FatalError("out of memory in Reporter");
+    if ( req_buffer_size < 0 ) {
+        va_end(ap_copy);
+        FatalError("out of memory in Reporter");
     }
 
+    if ( postfix && *postfix )
+        req_buffer_size += strlen(postfix) + 10;
+
+    // Add one byte for a null terminator.
+    req_buffer_size++;
+
+    if ( req_buffer_size > DEFAULT_BUFFER_SIZE ) {
+        buffer = (char*)malloc(req_buffer_size);
+        if ( ! buffer ) {
+            va_end(ap_copy);
+            FatalError("out of memory in Reporter");
+        }
+
+        allocated = buffer;
+    }
+
+    va_end(ap_copy);
+
+    req_buffer_size = vsnprintf(buffer, req_buffer_size, fmt, ap);
+    if ( req_buffer_size < 0 )
+        FatalError("out of memory in Reporter");
+
     if ( postfix && *postfix )
         // Note, if you change this fmt string, adjust the additional
         // buffer size above.
@@ -641,6 +653,7 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out, Conne
 #endif
     }
 
+    // If the buffer got reallocated because it was too small, free the reallocated one.
     if ( allocated )
         free(allocated);
 }