Use RAII to unmap or close the lexer states' files automatically

include/asm/lexer.hpp

@@ -83,6 +83,17 @@ struct LexerState {
 	std::deque<Expansion> expansions; // Front is the innermost current expansion
 
 	std::variant<std::monostate, MmappedLexerState, ViewedLexerState, BufferedLexerState> content;
+
+	LexerState() = default;
+	LexerState(LexerState &&) = default;
+	LexerState(LexerState const &) = delete;
+
+	// This destructor unmaps or closes the content file if applicable.
+	// As such, lexer states should not be copyable.
+	~LexerState();
+
+	LexerState &operator=(LexerState &&) = default;
+	LexerState &operator=(LexerState const &) = delete;
 };
 
 extern LexerState *lexerState;
@@ -117,7 +128,6 @@ void lexer_OpenFileView(
     LexerState &state, char const *path, char const *buf, size_t size, uint32_t lineNo
 );
 void lexer_RestartRept(uint32_t lineNo);
-void lexer_CleanupState(LexerState &state);
 void lexer_Init();
 void lexer_SetMode(LexerMode mode);
 void lexer_ToggleStringExpansion(bool enable);

src/asm/fstack.cpp

@@ -220,7 +220,6 @@ bool yywrap() {
 		return true;
 	}
 
-	lexer_CleanupState(contextStack.top().lexerState);
 	contextStack.pop();
 	lexer_SetState(&contextStack.top().lexerState);
 

src/asm/lexer.cpp

@@ -459,7 +459,7 @@ void lexer_RestartRept(uint32_t lineNo) {
 	lexerState->lineNo = lineNo;
 }
 
-void lexer_CleanupState(LexerState &state) {
+LexerState::~LexerState() {
 	// A big chunk of the lexer state soundness is the file stack ("fstack").
 	// Each context in the fstack has its own *unique* lexer state; thus, we always guarantee
 	// that lexer states lifetimes are always properly managed, since they're handled solely
@@ -471,12 +471,12 @@ void lexer_CleanupState(LexerState &state) {
 	// This assertion checks that this doesn't happen again.
 	// It could be argued that deleting a state that's scheduled for EOF could simply clear
 	// `lexerStateEOL`, but there's currently no situation in which this should happen.
-	assert(&state != lexerStateEOL);
+	assert(this != lexerStateEOL);
 
-	if (auto *mmap = std::get_if<MmappedLexerState>(&state.content); mmap) {
+	if (auto *mmap = std::get_if<MmappedLexerState>(&content); mmap) {
 		if (!mmap->isReferenced)
 			munmap(mmap->ptr, mmap->size);
-	} else if (auto *cbuf = std::get_if<BufferedLexerState>(&state.content); cbuf) {
+	} else if (auto *cbuf = std::get_if<BufferedLexerState>(&content); cbuf) {
 		close(cbuf->fd);
 	}
 }