From 0949b183d78986b503770c586cc5f06445bdacd3 Mon Sep 17 00:00:00 2001
From: Augusto Gunsch <augustogunsch@tutanota.com>
Date: Thu, 7 Jan 2021 19:58:28 -0300
Subject: [PATCH] Force last function statement to be 'return'

---
 compiler/compiler-statements.c | 12 ++++++++++++
 compiler/compiler-statements.h |  1 +
 compiler/compiler-structure.c  | 27 +++++++++++++++++++++------
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/compiler/compiler-statements.c b/compiler/compiler-statements.c
index f25adcc..3c40a37 100644
--- a/compiler/compiler-statements.c
+++ b/compiler/compiler-statements.c
@@ -169,3 +169,15 @@ LINEBLOCK* compilestatements(SCOPE* s, STATEMENT* sts) {
 	}
 	return head;
 }
+
+LINEBLOCK* compilestatementsretlast(SCOPE* s, STATEMENT* sts, STATEMENT** retlast) {
+	LINEBLOCK* head = NULL;
+	STATEMENT* last = NULL;
+	while(sts != NULL) {
+		head = mergelnblks(head, compilestatement(s, sts));
+		last = sts;
+		sts = sts->next;
+	}
+	*retlast = last;
+	return head;
+}
diff --git a/compiler/compiler-statements.h b/compiler/compiler-statements.h
index f71273b..a2868f3 100644
--- a/compiler/compiler-statements.h
+++ b/compiler/compiler-statements.h
@@ -6,4 +6,5 @@
  * Single function for compiling statements */
 
 LINEBLOCK* compilestatements(SCOPE* s, STATEMENT* sts);
+LINEBLOCK* compilestatementsretlast(SCOPE* s, STATEMENT* sts, STATEMENT** retlast);
 #endif
diff --git a/compiler/compiler-structure.c b/compiler/compiler-structure.c
index 9fa5bb6..a029282 100644
--- a/compiler/compiler-structure.c
+++ b/compiler/compiler-structure.c
@@ -12,7 +12,7 @@ int getobjsize(CLASS* c);
 LINE* mksubdeclabel(CLASS* c, SUBROUTDEC* sd);
 
 // Compiling methods
-LINEBLOCK* compilefunbody(SCOPE* s, CLASS* cl, SUBROUTBODY* b);
+LINEBLOCK* compilefunbody(SCOPE* s, CLASS* cl, SUBROUTDEC* d);
 LINEBLOCK* compilefundec(SCOPE* s, CLASS* cl, SUBROUTDEC* f);
 LINEBLOCK* compileconstructor(SCOPE* s, CLASS* cl, SUBROUTDEC* con);
 LINEBLOCK* compilemethod(SCOPE* s, CLASS* cl, SUBROUTDEC* m);
@@ -64,12 +64,27 @@ LINE* mksubdeclabel(CLASS* c, SUBROUTDEC* sd) {
 }
 
 // Compiling methods
-LINEBLOCK* compilefunbody(SCOPE* s, CLASS* cl, SUBROUTBODY* b) {
+LINEBLOCK* compilefunbody(SCOPE* s, CLASS* cl, SUBROUTDEC* d) {
+	SUBROUTBODY* b = d->body;
 	SCOPE* myscope = mkscope(s);
 	myscope->currclass = cl;
 	if(b->vardecs != NULL)
 		addlocalvars(myscope, b->vardecs);
-	LINEBLOCK* head = compilestatements(myscope, b->statements);
+
+	if(b->statements == NULL) {
+		eprintf("Subroutine body has no statements; file '%s', line %i\n",
+				d->debug->file, d->debug->definedat);
+		exit(1);
+	}
+
+	STATEMENT* last;
+	LINEBLOCK* head = compilestatementsretlast(myscope, b->statements, &last);
+	if(last->type != returnstatement) {
+		eprintf("Subroutine must end with a return statement; file '%s', line %i\n",
+				last->debug->file, last->debug->definedat);
+		exit(1);
+	}
+
 	freescope(myscope);
 	return head;
 }
@@ -78,7 +93,7 @@ LINEBLOCK* compilefundec(SCOPE* s, CLASS* cl, SUBROUTDEC* f) {
 	LINE* label = mksubdeclabel(cl, f);
 
 	if(f->body->statements != NULL) {
-		LINEBLOCK* body = compilefunbody(s, cl, f->body);
+		LINEBLOCK* body = compilefunbody(s, cl, f);
 		appendlnbefore(body, label);
 		return body;
 	}
@@ -99,7 +114,7 @@ LINEBLOCK* compileconstructor(SCOPE* s, CLASS* cl, SUBROUTDEC* con) {
 	free(size[2]);
 
 	if(con->body != NULL)
-		return mergelnblks(blk, compilefunbody(s, cl, con->body));
+		return mergelnblks(blk, compilefunbody(s, cl, con));
 	else
 		return blk;
 }
@@ -114,7 +129,7 @@ LINEBLOCK* compilemethod(SCOPE* s, CLASS* cl, SUBROUTDEC* m) {
 	appendln(blk, mkln(poppointer));
 
 	if(m->body != NULL) 
-		return mergelnblks(blk, compilefunbody(s, cl, m->body));
+		return mergelnblks(blk, compilefunbody(s, cl, m));
 	else
 		return blk;
 }