From 65f3a0171e25075db886f4d5cc4127ed04a77a88 Mon Sep 17 00:00:00 2001
From: Wilfred Hughes <me@wilfred.me.uk>
Date: Sat, 12 Jul 2014 01:05:17 +0100
Subject: [PATCH] Actually compiling return codes!

---
 minimal_c.l         | 7 ++++++-
 minimal_c.y         | 9 +++++++--
 test_programs/two.c | 3 +++
 3 files changed, 16 insertions(+), 3 deletions(-)
 create mode 100644 test_programs/two.c

diff --git a/minimal_c.l b/minimal_c.l
index f6317eb..d47f99d 100644
--- a/minimal_c.l
+++ b/minimal_c.l
@@ -13,7 +13,12 @@
 "("           { return '('; }
 ")"           { return ')'; }
 ";"           { return ';'; }
-[0-9]+        { return NUMBER; }
+[0-9]+        {
+                /* TODO: check numbers are in the legal range, and don't start with 0. */
+                printf("yytext: %s\n", yytext);
+                printf("yylval: %d\n", atoi(yytext));
+                yylval=atoi(yytext); return NUMBER;
+              }
 "return"      { return RETURN; }
 
 "int"         { return TYPE; }
diff --git a/minimal_c.y b/minimal_c.y
index 2b7593b..1c3f547 100644
--- a/minimal_c.y
+++ b/minimal_c.y
@@ -14,6 +14,9 @@ int yywrap()
 
 extern FILE *yyin;
 
+// Shameful hack. We should build a proper AST and traverse it.
+static int return_code;
+
 void write_skeleton() {
     FILE *out = fopen("out.s", "wb");
 
@@ -22,8 +25,9 @@ void write_skeleton() {
     fprintf(out, "    .global _start\n\n");
     fprintf(out, "_start:\n");
 
-    // Exit code of zero.
-    fprintf(out, "    movl    $0, %%ebx\n");
+    // Exit code as specified.
+    // TODO: convert to hex properly.
+    fprintf(out, "    movl    $%d, %%ebx\n", return_code);
 
     fprintf(out, "    movl    $1, %%eax\n");
     fprintf(out, "    int     $0x80\n");
@@ -73,5 +77,6 @@ function:
 
 expression:
 	RETURN NUMBER ';'
+        { return_code = $2; }
         ;
 
diff --git a/test_programs/two.c b/test_programs/two.c
new file mode 100644
index 0000000..5cca8e2
--- /dev/null
+++ b/test_programs/two.c
@@ -0,0 +1,3 @@
+int main() {
+    return 2;
+}