From 3b092bd9b6b3953d5c3052d57e4827dbd85941fd Mon Sep 17 00:00:00 2001
From: "Wladimir J. van der Laan" <laanwj@gmail.com>
Date: Thu, 9 Mar 2017 10:37:45 +0000
Subject: [PATCH] util: Properly handle errors during log message formatting

Instead of having an exception propagate into the program when an
error happens while formatting a log message, just print a message to
the log.

Addresses #9423.
---
 src/util.h | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/util.h b/src/util.h
index e27ce121c..c9d465954 100644
--- a/src/util.h
+++ b/src/util.h
@@ -73,14 +73,24 @@ bool LogAcceptCategory(const char* category);
 /** Send a string to the log output */
 int LogPrintStr(const std::string &str);
 
-#define LogPrint(category, ...) do { \
-    if (LogAcceptCategory((category))) { \
-        LogPrintStr(tfm::format(__VA_ARGS__)); \
-    } \
-} while(0)
+/** Get format string from VA_ARGS for error reporting */
+template<typename... Args> std::string FormatStringFromLogArgs(const char *fmt, const Args&... args) { return fmt; }
 
 #define LogPrintf(...) do { \
-    LogPrintStr(tfm::format(__VA_ARGS__)); \
+    std::string _log_msg_; /* Unlikely name to avoid shadowing variables */ \
+    try { \
+        _log_msg_ = tfm::format(__VA_ARGS__); \
+    } catch (std::runtime_error &e) { \
+        /* Original format string will have newline so don't add one here */ \
+        _log_msg_ = "Error \"" + std::string(e.what()) + "\" while formatting log message: " + FormatStringFromLogArgs(__VA_ARGS__); \
+    } \
+    LogPrintStr(_log_msg_); \
+} while(0)
+
+#define LogPrint(category, ...) do { \
+    if (LogAcceptCategory((category))) { \
+        LogPrintf(__VA_ARGS__); \
+    } \
 } while(0)
 
 template<typename... Args>