Suppress some GCC false-positive warnings (#896)

Author: HyunjinX917

CHANGELOG.md

@@ -101,6 +101,7 @@
 - Fixed thread-local context duplication across shared libraries ([#890](https://github.com/odygrd/quill/issues/890))
 - Added a `nullptr` check in macro-free log functions (`LogFunctions.h`) to allow calls with an uninitialized logger.
   Macro-based logging remains deliberately unchanged ([#894](https://github.com/odygrd/quill/issues/894))
+- Suppress GCC false-positive warnings during LTO builds.
 
 ## v11.0.2
 

include/quill/core/Codec.h

@@ -99,6 +99,9 @@ QUILL_NODISCARD inline size_t safe_strnlen(char const* str, size_t maxlen) noexc
   #if __GNUC__ >= 13
     #pragma GCC diagnostic ignored "-Wstringop-overread"
   #endif
+
+  // Suppress during LTO analysis
+  asm volatile("" : "+r"(maxlen) : : "memory");
 #endif
 
   auto end = static_cast<char const*>(std::memchr(str, '\0', maxlen));

include/quill/core/LoggerBase.h

@@ -117,7 +117,15 @@ class LoggerBase
    */
   QUILL_NODISCARD LogLevel get_log_level() const noexcept
   {
-    return _log_level.load(std::memory_order_relaxed);
+    auto const* self = this;
+
+#if defined(__GNUC__) && !defined(__clang__)
+    // GCC warns about potential null pointer access when logger might be
+    // uninitialized during LTO analysis
+    asm volatile("" : "+r"(self) : : "memory");
+#endif
+    
+    return self->_log_level.load(std::memory_order_relaxed);
   }
 
   /**