-Wexport-undefined warning for exporting undefined symbols

src/asm/symbol.cpp

@@ -611,7 +611,7 @@ void sym_Export(std::string const &symName) {
 	if (symName.starts_with('!')) {
 		// LCOV_EXCL_START
 		// The parser does not accept anonymous labels for an `EXPORT` directive
-		error("Anonymous labels cannot be exported");
+		error("Cannot export anonymous label");
 		return;
 		// LCOV_EXCL_STOP
 	}
@@ -620,8 +620,10 @@ void sym_Export(std::string const &symName) {
 
 	// If the symbol doesn't exist, create a ref that can be purged
 	if (!sym) {
+		warning(WARNING_EXPORT_UNDEFINED, "Exporting an undefined symbol `%s`", symName.c_str());
 		sym = sym_Ref(symName);
 	}
+
 	sym->isExported = true;
 }
 

src/asm/warning.cpp

@@ -30,6 +30,7 @@ Diagnostics<WarningLevel, WarningID> warnings = {
         {"empty-data-directive", LEVEL_ALL       },
         {"empty-macro-arg",      LEVEL_EXTRA     },
         {"empty-strrpl",         LEVEL_ALL       },
+        {"export-undefined",     LEVEL_ALL       },
         {"large-constant",       LEVEL_DEFAULT   },
         {"macro-shift",          LEVEL_EXTRA     },
         {"nested-comment",       LEVEL_DEFAULT   },