Output exported numeric constants to sym file (#1439)

include/asm/symbol.hpp

@@ -68,7 +68,7 @@ struct Symbol {
 	uint32_t getConstantValue() const;
 };
 
-void sym_ForEach(void (*func)(Symbol &));
+void sym_ForEach(void (*callback)(Symbol &));
 
 void sym_SetExportAll(bool set);
 Symbol *sym_AddLocalLabel(std::string const &symName);

include/link/symbol.hpp

@@ -38,6 +38,8 @@ struct Symbol {
 	Label const &label() const;
 };
 
+void sym_ForEach(void (*callback)(Symbol &));
+
 void sym_AddSymbol(Symbol &symbol);
 
 /*

man/rgblink.1

@@ -78,7 +78,9 @@ If specified, the map file will not list symbols, only sections.
 .It Fl m Ar map_file , Fl \-map Ar map_file
 Write a map file to the given filename, listing how sections and symbols were assigned.
 .It Fl n Ar sym_file , Fl \-sym Ar sym_file
-Write a symbol file to the given filename, listing the address of all exported symbols.
+Write a symbol file to the given filename, listing all visible labels and exported numeric constants.
+Labels output their bank and address, numeric constants output their value, following
+.Lk https://rgbds.gbdev.io/sym/ this specification .
 Several external programs can use this information, for example to help debugging ROMs.
 .It Fl O Ar overlay_file , Fl \-overlay Ar overlay_file
 If specified, sections will be overlaid "on top" of the ROM image

src/link/output.cpp

@@ -558,6 +558,25 @@ static void writeSym() {
 		for (uint32_t bank = 0; bank < sections[type].size(); bank++)
 			writeSymBank(sections[type][bank], type, bank);
 	}
+
+	// Output the exported numeric constants
+	static std::vector<Symbol *> constants; // `static` so `sym_ForEach` callback can see it
+	constants.clear();
+	sym_ForEach([](Symbol &sym) {
+		// Symbols are already limited to the exported ones
+		if (std::holds_alternative<int32_t>(sym.data))
+			constants.push_back(&sym);
+	});
+	// Numeric constants are ordered by value, then by name
+	std::sort(RANGE(constants), [](Symbol *sym1, Symbol *sym2) -> bool {
+		int32_t val1 = std::get<int32_t>(sym1->data), val2 = std::get<int32_t>(sym2->data);
+		return val1 != val2 ? val1 < val2 : sym1->name < sym2->name;
+	});
+	for (Symbol *sym : constants) {
+		int32_t val = std::get<int32_t>(sym->data);
+		int width = val < 0x100 ? 2 : val < 0x10000 ? 4 : 8;
+		fprintf(symFile, "%0*" PRIx32 " %s\n", width, val, sym->name.c_str());
+	}
 }
 
 // Writes the map file, if applicable.

src/link/symbol.cpp

@@ -22,6 +22,11 @@ Label const &Symbol::label() const {
 	return std::get<Label>(data);
 }
 
+void sym_ForEach(void (*callback)(Symbol &)) {
+	for (auto &it : symbols)
+		callback(*it.second);
+}
+
 void sym_AddSymbol(Symbol &symbol) {
 	Symbol *other = sym_GetSymbol(symbol.name);
 	auto *symValue = std::get_if<int32_t>(&symbol.data);