diff --git a/backends/cxxrtl/cxxrtl_backend.cc b/backends/cxxrtl/cxxrtl_backend.cc
index 7080f54d5..0c9f6c054 100644
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@@ -3478,8 +3478,8 @@ struct CxxrtlWorker {
 };
 
 struct CxxrtlBackend : public Backend {
-	static const int DEFAULT_OPT_LEVEL = 6;
-	static const int DEFAULT_DEBUG_LEVEL = 4;
+	static constexpr int DEFAULT_OPT_LEVEL = 6;
+	static constexpr int DEFAULT_DEBUG_LEVEL = 4;
 
 	CxxrtlBackend() : Backend("cxxrtl", "convert design to C++ RTL simulation") { }
 	void help() override
diff --git a/kernel/io.h b/kernel/io.h
index 08c234d6e..2ad0a6466 100644
--- a/kernel/io.h
+++ b/kernel/io.h
@@ -437,6 +437,7 @@ public:
 	{
 		return format_emit_toplevel(fmt, has_escapes, specs, args...);
 	}
+	std::string_view format_string() const { return fmt; }
 private:
 	std::string_view fmt;
 	bool has_escapes = false;
diff --git a/kernel/log.cc b/kernel/log.cc
index 1cd4a5449..0afc98cd0 100644
--- a/kernel/log.cc
+++ b/kernel/log.cc
@@ -102,17 +102,16 @@ int gettimeofday(struct timeval *tv, struct timezone *tz)
 }
 #endif
 
-static void logv(const char *format, va_list ap)
-{
-	while (format[0] == '\n' && format[1] != 0) {
-		log("\n");
-		format++;
+static void logv_string(std::string_view format, std::string str) {
+	size_t remove_leading = 0;
+	while (format.size() > 1 && format[0] == '\n') {
+		logv_string("\n", "\n");
+		format = format.substr(1);
+		++remove_leading;
+	}
+	if (remove_leading > 0) {
+		str = str.substr(remove_leading);
 	}
-
-	if (log_make_debug && !ys_debug(1))
-		return;
-
-	std::string str = vstringf(format, ap);
 
 	if (str.empty())
 		return;
@@ -145,13 +144,13 @@ static void logv(const char *format, va_list ap)
 			time_str += stringf("[%05d.%06d] ", int(tv.tv_sec), int(tv.tv_usec));
 		}
 
-		if (format[0] && format[strlen(format)-1] == '\n')
+		if (!format.empty() && format[format.size() - 1] == '\n')
 			next_print_log = true;
 
 		// Special case to detect newlines in Python log output, since
 		// the binding always calls `log("%s", payload)` and the newline
 		// is then in the first formatted argument
-		if (!strcmp(format, "%s") && str.back() == '\n')
+		if (format == "%s" && str.back() == '\n')
 			next_print_log = true;
 
 		for (auto f : log_files)
@@ -204,6 +203,20 @@ static void logv(const char *format, va_list ap)
 	}
 }
 
+static void logv(const char *format, va_list ap)
+{
+	if (log_make_debug && !ys_debug(1))
+		return;
+	logv_string(format, vstringf(format, ap));
+}
+
+void log_formatted_string(std::string_view format, std::string str)
+{
+	if (log_make_debug && !ys_debug(1))
+		return;
+	logv_string(format, std::move(str));
+}
+
 static void logv_header(RTLIL::Design *design, const char *format, va_list ap)
 {
 	bool pop_errfile = false;
@@ -412,14 +425,6 @@ void log_file_error(const string &filename, int lineno,
 	logv_file_error(filename, lineno, format, ap);
 }
 
-void log(const char *format, ...)
-{
-	va_list ap;
-	va_start(ap, format);
-	logv(format, ap);
-	va_end(ap);
-}
-
 void log_header(RTLIL::Design *design, const char *format, ...)
 {
 	va_list ap;
diff --git a/kernel/log.h b/kernel/log.h
index 27ee49d8f..f58bf3afe 100644
--- a/kernel/log.h
+++ b/kernel/log.h
@@ -121,7 +121,7 @@ extern int log_debug_suppressed;
 
 [[noreturn]] void logv_file_error(const string &filename, int lineno, const char *format, va_list ap);
 
-void log(const char *format, ...)  YS_ATTRIBUTE(format(printf, 1, 2));
+
 void log_header(RTLIL::Design *design, const char *format, ...) YS_ATTRIBUTE(format(printf, 2, 3));
 void log_warning(const char *format, ...) YS_ATTRIBUTE(format(printf, 1, 2));
 void log_experimental(const char *format, ...) YS_ATTRIBUTE(format(printf, 1, 2));
@@ -145,6 +145,15 @@ static inline bool ys_debug(int = 0) { return false; }
 #endif
 #  define log_debug(...) do { if (ys_debug(1)) log(__VA_ARGS__); } while (0)
 
+void log_formatted_string(std::string_view format, std::string str);
+template <typename... Args>
+inline void log(FmtString<TypeIdentity<Args>...> fmt, const Args &... args)
+{
+	if (log_make_debug && !ys_debug(1))
+		return;
+	log_formatted_string(fmt.format_string(), fmt.format(args...));
+}
+
 static inline void log_suppressed() {
 	if (log_debug_suppressed && !log_make_debug) {
 		log("<suppressed ~%d debug messages>\n", log_debug_suppressed);
@@ -346,8 +355,22 @@ static inline void log_dump_val_worker(unsigned long int v) { log("%lu", v); }
 static inline void log_dump_val_worker(long long int v) { log("%lld", v); }
 static inline void log_dump_val_worker(unsigned long long int v) { log("%lld", v); }
 #endif
-static inline void log_dump_val_worker(char c) { log(c >= 32 && c < 127 ? "'%c'" : "'\\x%02x'", c); }
-static inline void log_dump_val_worker(unsigned char c) { log(c >= 32 && c < 127 ? "'%c'" : "'\\x%02x'", c); }
+static inline void log_dump_val_worker(char c)
+{
+	if (c >= 32 && c < 127) {
+		log("'%c'", c);
+	} else {
+		log("'\\x%02x'", c);
+	}
+}
+static inline void log_dump_val_worker(unsigned char c)
+{
+	if (c >= 32 && c < 127) {
+		log("'%c'", c);
+	} else {
+		log("'\\x%02x'", c);
+	}
+}
 static inline void log_dump_val_worker(bool v) { log("%s", v ? "true" : "false"); }
 static inline void log_dump_val_worker(double v) { log("%f", v); }
 static inline void log_dump_val_worker(char *v) { log("%s", v); }
@@ -369,7 +392,7 @@ static inline void log_dump_val_worker(dict<K, T> &v) {
 	log("{");
 	bool first = true;
 	for (auto &it : v) {
-		log(first ? " " : ", ");
+		log("%s ", first ? "" : ",");
 		log_dump_val_worker(it.first);
 		log(": ");
 		log_dump_val_worker(it.second);
@@ -383,7 +406,7 @@ static inline void log_dump_val_worker(pool<K> &v) {
 	log("{");
 	bool first = true;
 	for (auto &it : v) {
-		log(first ? " " : ", ");
+		log("%s ", first ? "" : ",");
 		log_dump_val_worker(it);
 		first = false;
 	}
@@ -395,7 +418,7 @@ static inline void log_dump_val_worker(std::vector<K> &v) {
 	log("{");
 	bool first = true;
 	for (auto &it : v) {
-		log(first ? " " : ", ");
+		log("%s ", first ? "" : ",");
 		log_dump_val_worker(it);
 		first = false;
 	}
diff --git a/passes/cmds/logcmd.cc b/passes/cmds/logcmd.cc
index 0238627d1..391eaea2e 100644
--- a/passes/cmds/logcmd.cc
+++ b/passes/cmds/logcmd.cc
@@ -101,13 +101,13 @@ struct LogPass : public Pass {
 			text += args[argidx] + ' ';
 		if (!text.empty()) text.resize(text.size()-1);
 
-		const char *fmtline = newline ? "%s\n" : "%s";
+		const char *line_end = newline ? "\n" : "";
 
-		if (to_stdout) fprintf(stdout, fmtline, text.c_str());
-		if (to_stderr) fprintf(stderr, fmtline, text.c_str());
+		if (to_stdout) fprintf(stdout, "%s%s", text.c_str(), line_end);
+		if (to_stderr) fprintf(stderr, "%s%s", text.c_str(), line_end);
 		if (to_log) {
-			if (!header) log(fmtline, text.c_str());
-			else log_header(design, fmtline, text.c_str());
+			if (!header) log("%s%s", text.c_str(), line_end);
+			else log_header(design, "%s%s", text.c_str(), line_end);
 		}
 	}
 } LogPass;
diff --git a/passes/cmds/stat.cc b/passes/cmds/stat.cc
index ebbd10b5c..9281f3327 100644
--- a/passes/cmds/stat.cc
+++ b/passes/cmds/stat.cc
@@ -1017,7 +1017,7 @@ struct StatPass : public Pass {
 
 		if (json_mode) {
 			log("\n");
-			log(top_mod == nullptr ? "   }\n" : "   },\n");
+			log("%s", top_mod == nullptr ? "   }\n" : "   },\n");
 		}
 
 		if (top_mod != nullptr) {
diff --git a/passes/equiv/equiv_simple.cc b/passes/equiv/equiv_simple.cc
index 8ba42595e..9e3076077 100644
--- a/passes/equiv/equiv_simple.cc
+++ b/passes/equiv/equiv_simple.cc
@@ -331,7 +331,7 @@ struct EquivSimpleWorker
 			construct_ezsat(input_bits, step);
 
 			if (!ez->solve(ez_context)) {
-				log(cfg.verbose ? "    Proved equivalence! Marking $equiv cell as proven.\n" : " success!\n");
+				log("%s", cfg.verbose ? "    Proved equivalence! Marking $equiv cell as proven.\n" : " success!\n");
 				// Replace $equiv cell with a short
 				cell->setPort(ID::B, cell->getPort(ID::A));
 				ez->assume(ez->NOT(ez_context));
diff --git a/passes/sat/sat.cc b/passes/sat/sat.cc
index 2f20880cb..60e099097 100644
--- a/passes/sat/sat.cc
+++ b/passes/sat/sat.cc
@@ -634,10 +634,10 @@ struct SatHelper
 						    "---------------------------------------------------------------------------------------------------"
 						    "---------------------------------------------------------------------------------------------------";
 				if (last_timestep == -2) {
-					log(max_timestep > 0 ? "  Time " : "  ");
+					log("%s", max_timestep > 0 ? "  Time " : "  ");
 					log("%-*s %11s %9s %*s\n", maxModelName+5, "Signal Name", "Dec", "Hex", maxModelWidth+3, "Bin");
 				}
-				log(max_timestep > 0 ? "  ---- " : "  ");
+				log("%s", max_timestep > 0 ? "  ---- " : "  ");
 				log("%*.*s %11.11s %9.9s %*.*s\n", maxModelName+5, maxModelName+5,
 						hline, hline, hline, maxModelWidth+3, maxModelWidth+3, hline);
 				last_timestep = info.timestep;
diff --git a/passes/techmap/dfflibmap.cc b/passes/techmap/dfflibmap.cc
index a2b9c3bff..70d0f4ef5 100644
--- a/passes/techmap/dfflibmap.cc
+++ b/passes/techmap/dfflibmap.cc
@@ -135,7 +135,7 @@ static bool parse_next_state(const LibertyAst *cell, const LibertyAst *attr, std
 	if (ff == nullptr || ff->args.size() != 2)
 		return false;
 	auto ff_output = ff->args.at(0);
-	
+
 	// This test is redundant with the one in enable_pin, but we're in a
 	// position that gives better diagnostics here.
 	if (!pin_names.count(ff_output)) {
@@ -166,23 +166,23 @@ static bool parse_next_state(const LibertyAst *cell, const LibertyAst *attr, std
 		// the ff output Q is in a known bit location, so we now just have to compare the LUT mask to known values to find the enable pin and polarity.
 		if (lut == 0xD8) {
 			data_name = pins[1];
-			enable_name = pins[0];	
+			enable_name = pins[0];
 			return true;
 		}
 		if (lut == 0xB8) {
 			data_name = pins[0];
-			enable_name = pins[1];	
+			enable_name = pins[1];
 			return true;
 		}
 		enable_not_inverted = false;
 		if (lut == 0xE4) {
 			data_name = pins[1];
-			enable_name = pins[0];	
+			enable_name = pins[0];
 			return true;
 		}
 		if (lut == 0xE2) {
 			data_name = pins[0];
-			enable_name = pins[1];	
+			enable_name = pins[1];
 			return true;
 		}
 		// this does not match an enable flop.
@@ -553,11 +553,11 @@ static void dfflibmap(RTLIL::Design *design, RTLIL::Module *module)
 			new_cell->setPort("\\" + port.first, sig);
 		}
 
-		stats[stringf("  mapped %%d %s cells to %s cells.\n", cell_type, new_cell->type)]++;
+		stats[stringf("%s cells to %s cells", cell_type, new_cell->type)]++;
 	}
 
 	for (auto &stat: stats)
-		log(stat.first.c_str(), stat.second);
+		log("  mapped %d %s.\n", stat.second, stat.first);
 }
 
 struct DfflibmapPass : public Pass {
diff --git a/passes/tests/test_cell.cc b/passes/tests/test_cell.cc
index 87e0a00f8..a08a6ec29 100644
--- a/passes/tests/test_cell.cc
+++ b/passes/tests/test_cell.cc
@@ -620,7 +620,7 @@ static void run_eval_test(RTLIL::Design *design, bool verbose, bool nosat, std::
 
 	for (int i = 0; i < 64; i++)
 	{
-		log(verbose ? "\n" : ".");
+		log("%s", verbose ? "\n" : ".");
 		gold_ce.clear();
 		gate_ce.clear();