log: fix -Wformat-security lint and remove lint excuse

2 files changed, 26 insertions, 7 deletions

diff --git a/log.h b/log.h
index 6aca9ea..3e26501 100644
--- a/log.h
+++ b/log.h
@@ -75,6 +75,25 @@ constexpr inline Arg sanitize_fmt_args(Arg arg) {
   return arg;
 }
 
+template <std::size_t N>
+struct formatter {
+  template <typename... Args>
+  std::size_t operator()(char* str,
+                         std::size_t size,
+                         const char* fmt,
+                         Args... args) {
+    static_assert(sizeof...(Args) == N, "");
+    return std::snprintf(str, size, fmt, args...);
+  }
+};
+
+template <>
+struct formatter<0> {
+  std::size_t operator()(char* str, std::size_t size, const char* fmt) {
+    return std::snprintf(str, size, "%s", fmt);
+  }
+};
+
 // -- TIME STAMP HELPER --------------------------------------------------------
 
 template <int UtcOffset = 0>
@@ -112,7 +131,7 @@ struct time_stamp {
 
 // -- LOGGER -------------------------------------------------------------------
 
-template <bool WithTimestamp = true, size_t BufSize = 128>
+template <bool WithTimestamp = true, std::size_t BufSize = 128>
 struct logger {
   constexpr logger() = default;
   constexpr logger(log_level lvl) : m_lvl{lvl} {}
@@ -134,11 +153,11 @@ struct logger {
 
 // -- LOGGER IMPLEMENTATION ----------------------------------------------------
 
-template <bool WithTimestamp, size_t BufSize>
+template <bool WithTimestamp, std::size_t BufSize>
 template <log_level L, typename... Args>
 constexpr void logger<WithTimestamp, BufSize>::log(const char* fmt,
                                                    Args... args) {
-  size_t pos{0};
+  std::size_t pos{0};
 
   // Add timestamp if enabled.
   if (WithTimestamp) {
@@ -160,10 +179,9 @@ constexpr void logger<WithTimestamp, BufSize>::log(const char* fmt,
   // string literal as fmt string and hence the user controls the fmt string.
   // Additionally, we sanitize the arguments to only allow explicitly specified
   // argument types.
-  //
-  // NOLINTNEXTLINE
-  pos += std::snprintf(m_buf + pos, BufSize - pos, fmt,
-                       detail::sanitize_fmt_args(args)...);
+  detail::formatter<sizeof...(Args)> formatter;
+  pos += formatter(m_buf + pos, BufSize - pos, fmt,
+                   detail::sanitize_fmt_args(args)...);
   assert(pos < BufSize);
 
   // Ensure terminated with new line and null terminator.
diff --git a/test/log.cc b/test/log.cc
index c059ba8..7d8305d 100644
--- a/test/log.cc
+++ b/test/log.cc
@@ -4,6 +4,7 @@ int main() {
   logging::logger<> mlog;
   mlog.set_level(logging::kDbg0);
 
+  INFO(&mlog, "Hallo nofmt");
   INFO(&mlog, "Hallo %d", 42);
   WARN(&mlog, "Hallo %x", 0x1337);
   FAIL(&mlog, "Hallo %u", 666);