Add -B/--backtrace option to RGBASM and RGBLINK (#1787)

include/link/fstack.hpp

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: MIT
+
+#ifndef RGBDS_LINK_FSTACK_HPP
+#define RGBDS_LINK_FSTACK_HPP
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string>
+#include <variant>
+#include <vector>
+
+#include "linkdefs.hpp"
+
+struct FileStackNode {
+	FileStackNodeType type;
+	std::variant<
+	    std::monostate,        // Default constructed; `.type` and `.data` must be set manually
+	    std::vector<uint32_t>, // NODE_REPT
+	    std::string            // NODE_FILE, NODE_MACRO
+	    >
+	    data;
+
+	FileStackNode *parent;
+	// Line at which the parent context was exited; meaningless for the root level
+	uint32_t lineNo;
+
+	// REPT iteration counts since last named node, in reverse depth order
+	std::vector<uint32_t> &iters() { return std::get<std::vector<uint32_t>>(data); }
+	std::vector<uint32_t> const &iters() const { return std::get<std::vector<uint32_t>>(data); }
+	// File name for files, file::macro name for macros
+	std::string &name() { return std::get<std::string>(data); }
+	std::string const &name() const { return std::get<std::string>(data); }
+
+	void printBacktrace(uint32_t curLineNo) const;
+	std::vector<std::pair<std::string, uint32_t>> backtrace(uint32_t curLineNo) const;
+};
+
+#endif // RGBDS_LINK_FSTACK_HPP