From a75c766f80126525e8dfa525b32252ba38b17b26 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Sat, 30 Oct 2021 20:54:23 +0200
Subject: cc: some proper checking of return types and some primitive check for
 missing or superflous return statements

---
 miniany/cc.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'miniany/cc.c')

diff --git a/miniany/cc.c b/miniany/cc.c
index 44cdd76..22781a2 100644
--- a/miniany/cc.c
+++ b/miniany/cc.c
@@ -365,6 +365,7 @@ struct Symbol {
 	int type;		/* type of variable when class is SYMBOL_CLASS_VARIABLE */
 	struct Symbol *next;	/* pointer to next symbol */
 	int return_type;	/* return type when class is SYMBOL_CLASS_FUNCTION */
+	int seen_return;	/* whether we saw a return in the definiton of a function (SYMBOL_CLASS_FUNCTION) */
 };
 
 struct Symbol *createSymbol( int class, char *s )
@@ -526,6 +527,7 @@ struct Parser {
 	int token;
 	struct Scanner *scanner;
 	struct Scope *global_scope;
+	struct Symbol *current_function;
 	int debug;
 };
 
@@ -1099,6 +1101,7 @@ struct Parser *createParser( )
 	parser->scanner = createScanner( );
 	parser->global_scope = createScope( "global" );
 	parser->debug = 0;
+	parser->current_function = NULL;
 	
 	return parser;
 }
@@ -1561,11 +1564,30 @@ void parseDo( struct Compiler *compiler )
 void parseReturn( struct Compiler *compiler )
 {
 	struct Parser *parser;
+	struct Symbol *sym;
 	struct ASTnode *node;
 
 	parser = compiler->parser;
+	sym = parser->current_function;
+	if( sym == NULL ) {
+		scannerPrintErrorHeader( parser->scanner );
+		putstring( "return outside a function" );
+		putnl( );
+		exit( EXIT_FAILURE );	
+	}
+	if( sym->return_type == S_VOID ) {
+		scannerPrintErrorHeader( parser->scanner );
+		putstring( "return inside function '" ) ;
+		putstring( sym->name );
+		putstring( "' can not return any value" );
+		putnl( );
+		exit( EXIT_FAILURE );	
+	}
+	sym->seen_return = 1;
+		
 	parserExpect( parser, S_RETURN, "return" );
 	node = parseExpression( parser, 0 );
+	/* TODO: verify that sym->return_type fits to the type of the expression */
 	generateFromAST( compiler->generator, node, NOREG );
 	freeASTnode( node );
 	parserExpect( parser, S_SEMICOLON, ";" );
@@ -1632,6 +1654,8 @@ void parseFunctionDeclaration( struct Compiler *compiler )
 		sym = createSymbol( SYMBOL_CLASS_FUNCTION, parser->scanner->ident );
 		insertSymbol( parser->global_scope, sym );
 		sym->return_type = type;
+		sym->seen_return = 0;
+		parser->current_function = sym;
 	} else {
 		scannerPrintErrorHeader( parser->scanner );
 		putstring( "duplicate global symbol '" );
@@ -1653,7 +1677,18 @@ void parseFunctionDeclaration( struct Compiler *compiler )
 	parserExpect( parser, S_LPAREN, "(" );
 	/* TODO: parse parameter list */
 	parserExpect( parser, S_RPAREN, ")" );
+
 	parseStatementBlock( compiler );
+	
+	if( sym->return_type != S_VOID && !sym->seen_return ) {
+		scannerPrintErrorHeader( parser->scanner );
+		putstring( "return excpected in non-void function '" );
+		putstring( sym->name );
+		putstring( "'" );
+		putnl( );
+		exit( EXIT_FAILURE );
+	}
+		
 	putstring( "pop ebp" ); putnl( );
 	putstring( "ret" ); putnl( );
 	genFreeAllRegs( compiler->generator );
-- 
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