log: Use `__func__` for -logsourcelocations

diff --git a/doc/release-notes-34088.md b/doc/release-notes-34088.md
new file mode 100644
index 00000000..5aa8a9d9
--- /dev/null
+++ b/doc/release-notes-34088.md
@@ -0,0 +1,2 @@
+- When `-logsourcelocations` is enabled, the log output now contains just the
+  function name instead of the entire function signature. (#34088)
diff --git a/src/logging.cpp b/src/logging.cpp
index 5fb42bba..113fc346 100644
--- a/src/logging.cpp
+++ b/src/logging.cpp
@@ -75,7 +75,7 @@ bool BCLog::Logger::StartLogging()
     // dump buffered messages from before we opened the log
     m_buffering = false;
     if (m_buffer_lines_discarded > 0) {
-        LogPrintStr_(strprintf("Early logging buffer overflowed, %d log lines discarded.\n", m_buffer_lines_discarded), std::source_location::current(), BCLog::ALL, Level::Info, /*should_ratelimit=*/false);
+        LogPrintStr_(strprintf("Early logging buffer overflowed, %d log lines discarded.\n", m_buffer_lines_discarded), SourceLocation{__func__}, BCLog::ALL, Level::Info, /*should_ratelimit=*/false);
     }
     while (!m_msgs_before_open.empty()) {
         const auto& buflog = m_msgs_before_open.front();
@@ -388,7 +388,7 @@ std::shared_ptr<BCLog::LogRateLimiter> BCLog::LogRateLimiter::Create(
 }
 
 BCLog::LogRateLimiter::Status BCLog::LogRateLimiter::Consume(
-    const std::source_location& source_loc,
+    const SourceLocation& source_loc,
     const std::string& str)
 {
     StdLockGuard scoped_lock(m_mutex);
@@ -403,14 +403,14 @@ BCLog::LogRateLimiter::Status BCLog::LogRateLimiter::Consume(
     return status;
 }
 
-void BCLog::Logger::FormatLogStrInPlace(std::string& str, BCLog::LogFlags category, BCLog::Level level, const std::source_location& source_loc, std::string_view threadname, SystemClock::time_point now, std::chrono::seconds mocktime) const
+void BCLog::Logger::FormatLogStrInPlace(std::string& str, BCLog::LogFlags category, BCLog::Level level, const SourceLocation& source_loc, std::string_view threadname, SystemClock::time_point now, std::chrono::seconds mocktime) const
 {
     if (!str.ends_with('\n')) str.push_back('\n');
 
     str.insert(0, GetLogPrefix(category, level));
 
     if (m_log_sourcelocations) {
-        str.insert(0, strprintf("[%s:%d] [%s] ", RemovePrefixView(source_loc.file_name(), "./"), source_loc.line(), source_loc.function_name()));
+        str.insert(0, strprintf("[%s:%d] [%s] ", RemovePrefixView(source_loc.file_name(), "./"), source_loc.line(), source_loc.function_name_short()));
     }
 
     if (m_log_threadnames) {
@@ -420,14 +420,14 @@ void BCLog::Logger::FormatLogStrInPlace(std::string& str, BCLog::LogFlags catego
     str.insert(0, LogTimestampStr(now, mocktime));
 }
 
-void BCLog::Logger::LogPrintStr(std::string_view str, std::source_location&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
+void BCLog::Logger::LogPrintStr(std::string_view str, SourceLocation&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
 {
     StdLockGuard scoped_lock(m_cs);
     return LogPrintStr_(str, std::move(source_loc), category, level, should_ratelimit);
 }
 
 // NOLINTNEXTLINE(misc-no-recursion)
-void BCLog::Logger::LogPrintStr_(std::string_view str, std::source_location&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
+void BCLog::Logger::LogPrintStr_(std::string_view str, SourceLocation&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
 {
     std::string str_prefixed = LogEscapeMessage(str);
 
@@ -470,10 +470,10 @@ void BCLog::Logger::LogPrintStr_(std::string_view str, std::source_location&& so
                              "the last time window of %is. Suppressing logging to disk from this "
                              "source location until time window resets. Console logging "
                              "unaffected. Last log entry.",
-                             source_loc.file_name(), source_loc.line(), source_loc.function_name(),
+                             source_loc.file_name(), source_loc.line(), source_loc.function_name_short(),
                              m_limiter->m_max_bytes,
                              Ticks<std::chrono::seconds>(m_limiter->m_reset_window)),
-                         std::source_location::current(), LogFlags::ALL, Level::Warning, /*should_ratelimit=*/false); // with should_ratelimit=false, this cannot lead to infinite recursion
+                         SourceLocation{__func__}, LogFlags::ALL, Level::Warning, /*should_ratelimit=*/false); // with should_ratelimit=false, this cannot lead to infinite recursion
         } else if (status == LogRateLimiter::Status::STILL_SUPPRESSED) {
             ratelimit = true;
         }
@@ -564,7 +564,7 @@ void BCLog::LogRateLimiter::Reset()
         LogPrintLevel_(
             LogFlags::ALL, Level::Warning, /*should_ratelimit=*/false,
             "Restarting logging from %s:%d (%s): %d bytes were dropped during the last %ss.",
-            source_loc.file_name(), source_loc.line(), source_loc.function_name(),
+            source_loc.file_name(), source_loc.line(), source_loc.function_name_short(),
             stats.m_dropped_bytes, Ticks<std::chrono::seconds>(m_reset_window));
     }
 }
diff --git a/src/logging.h b/src/logging.h
index 29f51085..2105039f 100644
--- a/src/logging.h
+++ b/src/logging.h
@@ -37,15 +37,35 @@ extern const char * const DEFAULT_DEBUGLOGFILE;
 
 extern bool fLogIPs;
 
+/// Like std::source_location, but allowing to override the function name.
+class SourceLocation
+{
+public:
+    /// The func argument must be constructed from the C++11 __func__ macro.
+    /// Ref: https://en.cppreference.com/w/cpp/language/function.html#func
+    /// Non-static string literals are not supported.
+    SourceLocation(const char* func,
+                   std::source_location loc = std::source_location::current())
+        : m_func{func}, m_loc{loc} {}
+
+    std::string_view file_name() const { return m_loc.file_name(); }
+    std::uint_least32_t line() const { return m_loc.line(); }
+    std::string_view function_name_short() const { return m_func; }
+
+private:
+    std::string_view m_func;
+    std::source_location m_loc;
+};
+
 struct SourceLocationEqual {
-    bool operator()(const std::source_location& lhs, const std::source_location& rhs) const noexcept
+    bool operator()(const SourceLocation& lhs, const SourceLocation& rhs) const noexcept
     {
         return lhs.line() == rhs.line() && std::string_view(lhs.file_name()) == std::string_view(rhs.file_name());
     }
 };
 
 struct SourceLocationHasher {
-    size_t operator()(const std::source_location& s) const noexcept
+    size_t operator()(const SourceLocation& s) const noexcept
     {
         // Use CSipHasher(0, 0) as a simple way to get uniform distribution.
         return size_t(CSipHasher(0, 0)
@@ -131,7 +151,7 @@ namespace BCLog {
         mutable StdMutex m_mutex;
 
         //! Stats for each source location that has attempted to log something.
-        std::unordered_map<std::source_location, Stats, SourceLocationHasher, SourceLocationEqual> m_source_locations GUARDED_BY(m_mutex);
+        std::unordered_map<SourceLocation, Stats, SourceLocationHasher, SourceLocationEqual> m_source_locations GUARDED_BY(m_mutex);
         //! Whether any log locations are suppressed. Cached view on m_source_locations for performance reasons.
         std::atomic<bool> m_suppression_active{false};
         LogRateLimiter(uint64_t max_bytes, std::chrono::seconds reset_window);
@@ -163,7 +183,7 @@ namespace BCLog {
         //! Consumes `source_loc`'s available bytes corresponding to the size of the (formatted)
         //! `str` and returns its status.
         [[nodiscard]] Status Consume(
-            const std::source_location& source_loc,
+            const SourceLocation& source_loc,
             const std::string& str) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
         //! Resets all usage to zero. Called periodically by the scheduler.
         void Reset() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
@@ -178,7 +198,7 @@ namespace BCLog {
             SystemClock::time_point now;
             std::chrono::seconds mocktime;
             std::string str, threadname;
-            std::source_location source_loc;
+            SourceLocation source_loc;
             LogFlags category;
             Level level;
         };
@@ -206,7 +226,7 @@ namespace BCLog {
         /** Log categories bitfield. */
         std::atomic<CategoryMask> m_categories{BCLog::NONE};
 
-        void FormatLogStrInPlace(std::string& str, LogFlags category, Level level, const std::source_location& source_loc, std::string_view threadname, SystemClock::time_point now, std::chrono::seconds mocktime) const;
+        void FormatLogStrInPlace(std::string& str, LogFlags category, Level level, const SourceLocation& source_loc, std::string_view threadname, SystemClock::time_point now, std::chrono::seconds mocktime) const;
 
         std::string LogTimestampStr(SystemClock::time_point now, std::chrono::seconds mocktime) const;
 
@@ -214,7 +234,7 @@ namespace BCLog {
         std::list<std::function<void(const std::string&)>> m_print_callbacks GUARDED_BY(m_cs) {};
 
         /** Send a string to the log output (internal) */
-        void LogPrintStr_(std::string_view str, std::source_location&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
+        void LogPrintStr_(std::string_view str, SourceLocation&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
             EXCLUSIVE_LOCKS_REQUIRED(m_cs);
 
         std::string GetLogPrefix(LogFlags category, Level level) const;
@@ -233,7 +253,7 @@ namespace BCLog {
         std::atomic<bool> m_reopen_file{false};
 
         /** Send a string to the log output */
-        void LogPrintStr(std::string_view str, std::source_location&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
+        void LogPrintStr(std::string_view str, SourceLocation&& source_loc, BCLog::LogFlags category, BCLog::Level level, bool should_ratelimit)
             EXCLUSIVE_LOCKS_REQUIRED(!m_cs);
 
         /** Returns whether logs will be written to any output */
@@ -347,7 +367,7 @@ static inline bool LogAcceptCategory(BCLog::LogFlags category, BCLog::Level leve
 bool GetLogCategory(BCLog::LogFlags& flag, std::string_view str);
 
 template <typename... Args>
-inline void LogPrintFormatInternal(std::source_location&& source_loc, BCLog::LogFlags flag, BCLog::Level level, bool should_ratelimit, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
+inline void LogPrintFormatInternal(SourceLocation&& source_loc, BCLog::LogFlags flag, BCLog::Level level, bool should_ratelimit, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
 {
     if (LogInstance().Enabled()) {
         std::string log_msg;
@@ -360,7 +380,9 @@ inline void LogPrintFormatInternal(std::source_location&& source_loc, BCLog::Log
     }
 }
 
-#define LogPrintLevel_(category, level, should_ratelimit, ...) LogPrintFormatInternal(std::source_location::current(), category, level, should_ratelimit, __VA_ARGS__)
+// Allow __func__ to be used in any context without warnings:
+// NOLINTNEXTLINE(bugprone-lambda-function-name)
+#define LogPrintLevel_(category, level, should_ratelimit, ...) LogPrintFormatInternal(SourceLocation{__func__}, category, level, should_ratelimit, __VA_ARGS__)
 
 // Log unconditionally. Uses basic rate limiting to mitigate disk filling attacks.
 // Be conservative when using functions that unconditionally log to debug.log!
diff --git a/src/test/logging_tests.cpp b/src/test/logging_tests.cpp
index 2a34aefa..12ce40fb 100644
--- a/src/test/logging_tests.cpp
+++ b/src/test/logging_tests.cpp
@@ -118,21 +118,21 @@ BOOST_FIXTURE_TEST_CASE(logging_LogPrintStr, LogSetup)
         BCLog::LogFlags category;
         BCLog::Level level;
         std::string prefix;
-        std::source_location loc;
+        SourceLocation loc;
     };
 
     std::vector<Case> cases = {
-        {"foo1: bar1", BCLog::NET, BCLog::Level::Debug, "[net] ", std::source_location::current()},
-        {"foo2: bar2", BCLog::NET, BCLog::Level::Info, "[net:info] ", std::source_location::current()},
-        {"foo3: bar3", BCLog::ALL, BCLog::Level::Debug, "[debug] ", std::source_location::current()},
-        {"foo4: bar4", BCLog::ALL, BCLog::Level::Info, "", std::source_location::current()},
-        {"foo5: bar5", BCLog::NONE, BCLog::Level::Debug, "[debug] ", std::source_location::current()},
-        {"foo6: bar6", BCLog::NONE, BCLog::Level::Info, "", std::source_location::current()},
+        {"foo1: bar1", BCLog::NET, BCLog::Level::Debug, "[net] ", SourceLocation{__func__}},
+        {"foo2: bar2", BCLog::NET, BCLog::Level::Info, "[net:info] ", SourceLocation{__func__}},
+        {"foo3: bar3", BCLog::ALL, BCLog::Level::Debug, "[debug] ", SourceLocation{__func__}},
+        {"foo4: bar4", BCLog::ALL, BCLog::Level::Info, "", SourceLocation{__func__}},
+        {"foo5: bar5", BCLog::NONE, BCLog::Level::Debug, "[debug] ", SourceLocation{__func__}},
+        {"foo6: bar6", BCLog::NONE, BCLog::Level::Info, "", SourceLocation{__func__}},
     };
 
     std::vector<std::string> expected;
     for (auto& [msg, category, level, prefix, loc] : cases) {
-        expected.push_back(tfm::format("[%s:%s] [%s] %s%s", util::RemovePrefix(loc.file_name(), "./"), loc.line(), loc.function_name(), prefix, msg));
+        expected.push_back(tfm::format("[%s:%s] [%s] %s%s", util::RemovePrefix(loc.file_name(), "./"), loc.line(), loc.function_name_short(), prefix, msg));
         LogInstance().LogPrintStr(msg, std::move(loc), category, level, /*should_ratelimit=*/false);
     }
     std::vector<std::string> log_lines{ReadDebugLogLines()};
@@ -306,8 +306,8 @@ BOOST_AUTO_TEST_CASE(logging_log_rate_limiter)
     auto& limiter{*Assert(limiter_)};
 
     using Status = BCLog::LogRateLimiter::Status;
-    auto source_loc_1{std::source_location::current()};
-    auto source_loc_2{std::source_location::current()};
+    auto source_loc_1{SourceLocation{__func__}};
+    auto source_loc_2{SourceLocation{__func__}};
 
     // A fresh limiter should not have any suppressions
     BOOST_CHECK(!limiter.SuppressionsActive());