Merge #9963: util: Properly handle errors during log message formatting

b651270 util: Throw tinyformat::format_error on formatting error (Wladimir J. van der Laan)
3b092bd util: Properly handle errors during log message formatting (Wladimir J. van der Laan)

Tree-SHA512: 85e3b7afec2255fc88034187f1abd6060e9421de17ed4e3d918416f393429a99cc2c974b362099aaaff6970549df47664bea4c857c4e46acc0789663201dc541

Author: laanwj

src/tinyformat.h

@@ -123,7 +123,7 @@ namespace tinyformat {}
 namespace tfm = tinyformat;
 
 // Error handling; calls assert() by default.
-#define TINYFORMAT_ERROR(reasonString) throw std::runtime_error(reasonString)
+#define TINYFORMAT_ERROR(reasonString) throw tinyformat::format_error(reasonString)
 
 // Define for C++11 variadic templates which make the code shorter & more
 // general.  If you don't define this, C++11 support is autodetected below.
@@ -164,6 +164,13 @@ namespace tfm = tinyformat;
 
 namespace tinyformat {
 
+class format_error: public std::runtime_error
+{
+public:
+    format_error(const std::string &what): std::runtime_error(what) {
+    }
+};
+
 //------------------------------------------------------------------------------
 namespace detail {
 

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__)); \
+/** 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 { \
+    std::string _log_msg_; /* Unlikely name to avoid shadowing variables */ \
+    try { \
+        _log_msg_ = tfm::format(__VA_ARGS__); \
+    } catch (tinyformat::format_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 LogPrintf(...) do { \
-    LogPrintStr(tfm::format(__VA_ARGS__)); \
+#define LogPrint(category, ...) do { \
+    if (LogAcceptCategory((category))) { \
+        LogPrintf(__VA_ARGS__); \
+    } \
 } while(0)
 
 template<typename... Args>