util: add and use run-time safe tinyformat::try_format

In certain situations, such as logging, string formatting errors
should not cause application failures. We already use
util::ConstevalFormatString in those cases, to try and catch some
errors at compile-time.

Improve this further by suppressing run-time errors by returning
the error message instead of throwing a tinyformat::format_error.
This is done by taking the existing error handling in
LogPrintFormatInternal(), and move it to tfm::try_format().

src/index/base.cpp

@@ -30,7 +30,7 @@ constexpr auto SYNC_LOCATOR_WRITE_INTERVAL{30s};
 template <typename... Args>
 void BaseIndex::FatalErrorf(util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
-    auto message = tfm::format(fmt, args...);
+    auto message{tfm::try_format(fmt, args...)};
     node::AbortNode(m_chain->context()->shutdown, m_chain->context()->exit_status, Untranslated(message), m_chain->context()->warnings.get());
 }
 

src/logging.h

@@ -249,13 +249,7 @@ template <typename... Args>
 inline void LogPrintFormatInternal(std::string_view logging_function, std::string_view source_file, const int source_line, const BCLog::LogFlags flag, const BCLog::Level level, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
     if (LogInstance().Enabled()) {
-        std::string log_msg;
-        try {
-            log_msg = tfm::format(fmt, args...);
-        } catch (tinyformat::format_error& fmterr) {
-            /* Original format string will have newline so don't add one here */
-            log_msg = "Error \"" + std::string{fmterr.what()} + "\" while formatting log message: " + fmt.fmt;
-        }
+        const auto log_msg{tfm::try_format(fmt, args...)};
         LogInstance().LogPrintStr(log_msg, logging_function, source_file, source_line, flag, level);
     }
 }

src/netbase.cpp

@@ -559,7 +559,7 @@ std::function<std::unique_ptr<Sock>(int, int, int)> CreateSock = CreateSockOS;
 template<typename... Args>
 static void LogConnectFailure(bool manual_connection, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
-    std::string error_message = tfm::format(fmt, args...);
+    std::string error_message{tfm::try_format(fmt, args...)};
     if (manual_connection) {
         LogPrintf("%s\n", error_message);
     } else {

src/test/util_string_tests.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <tinyformat.h>
 #include <util/string.h>
 
 #include <boost/test/unit_test.hpp>
@@ -83,4 +84,12 @@ BOOST_AUTO_TEST_CASE(ConstevalFormatString_NumSpec)
     FailFmtWithError<1>("%1$", err_term);
 }
 
+BOOST_AUTO_TEST_CASE(tinyformat_try_format)
+{
+    // ensure invalid format strings don't throw at run-time
+    BOOST_CHECK_EQUAL(tfm::try_format("%*c", "dummy"), R"(Error "tinyformat: Cannot convert from argument type to integer for use as variable width or precision" while formatting log message: "%*c")");
+    BOOST_CHECK_EQUAL(tfm::try_format("%2$*3$d", "dummy", "value"), R"(Error "tinyformat: Positional argument out of range" while formatting log message: "%2$*3$d")");
+    BOOST_CHECK_EQUAL(tfm::try_format("%.*f", 5), R"(Error "tinyformat: Too many conversion specifiers in format string" while formatting log message: "%.*f")");
+}
+
 BOOST_AUTO_TEST_SUITE_END()

src/util/string.h

@@ -235,11 +235,25 @@ template <typename T1, size_t PREFIX_LEN>
 }
 } // namespace util
 
+/**
+ * Safer alternative to tfm::format that does not throw string
+ * formatting errors at run-time.
+ *
+ * The `fmt` format string is partially checked at compile-time. At
+ * run-time, if any `tinyformat::format_error` occurs, the error is caught
+ * and the error message is returned instead, so the caller doesn't need
+ * to handle the error.
+ */
 namespace tinyformat {
 template <typename... Args>
-std::string format(util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
+std::string try_format(util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
-    return format(fmt.fmt, args...);
+    try {
+        return tfm::format(fmt.fmt, args...);
+    } catch (tinyformat::format_error& fmterr) {
+        /* Original format string will have newline so don't add one here */
+        return "Error \"" + std::string{fmterr.what()} + "\" while formatting log message: \"" + fmt.fmt + "\"";
+    }
 }
 } // namespace tinyformat
 

src/wallet/scriptpubkeyman.h

@@ -256,7 +256,7 @@ class ScriptPubKeyMan
     template <typename... Params>
     void WalletLogPrintf(util::ConstevalFormatString<sizeof...(Params)> wallet_fmt, const Params&... params) const
     {
-        LogInfo("%s %s", m_storage.GetDisplayName(), tfm::format(wallet_fmt, params...));
+        LogInfo("%s %s", m_storage.GetDisplayName(), tfm::try_format(wallet_fmt, params...));
     };
 
     /** Watch-only address added */

src/wallet/wallet.h

@@ -929,7 +929,7 @@ class CWallet final : public WalletStorage, public interfaces::Chain::Notificati
     template <typename... Params>
     void WalletLogPrintf(util::ConstevalFormatString<sizeof...(Params)> wallet_fmt, const Params&... params) const
     {
-        LogInfo("%s %s", GetDisplayName(), tfm::format(wallet_fmt, params...));
+        LogInfo("%s %s", GetDisplayName(), tfm::try_format(wallet_fmt, params...));
     };
 
     /** Upgrade the wallet */