From bf2c6f765db1b349d5bd5ce98631144f9cab654a Mon Sep 17 00:00:00 2001
From: Johnny Richard <johnny@johnnyrichard.com>
Date: Sat, 15 Apr 2023 03:07:21 +0200
Subject: parser: Generate GAS 64-bit assembly for linux

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>
---
 HACKING            |  2 +-
 examples/main.pipa |  2 +-
 src/pipac.c        | 20 +++++++++++++++++++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/HACKING b/HACKING
index af95ec2..23a3a9f 100644
--- a/HACKING
+++ b/HACKING
@@ -2,4 +2,4 @@ HACKING
 -------
 
    $ make
-   $ ./pipac examples/main.pipa
+   $ ./pipac examples/main.pipa > main.s && as -64 -o main.o main.s && ld -o main main.o
diff --git a/examples/main.pipa b/examples/main.pipa
index 5767e09..6524bec 100644
--- a/examples/main.pipa
+++ b/examples/main.pipa
@@ -1,3 +1,3 @@
 main(): i32 {
-  return 1;
+  return 69;
 }
diff --git a/src/pipac.c b/src/pipac.c
index 29c21bd..993d56d 100644
--- a/src/pipac.c
+++ b/src/pipac.c
@@ -16,9 +16,27 @@
 */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+
 #include "lexer.h"
 #include "parser.h"
 
+void
+generate_gas_x86_64_linux(ast_function_t *func)
+{
+  if (strcmp(func->name, "main") != 0) {
+    fprintf(stderr, "[ERROR]: no main function has been defined!\n");
+    exit(EXIT_FAILURE);
+  }
+
+  printf(".global _start\n");
+  printf(".text\n");
+  printf("_start:\n");
+  printf("  mov $1, %%al\n");
+  printf("  mov $%d, %%ebx\n", func->body.number);
+  printf("  int $0x80\n");
+}
+
 void
 print_usage()
 {
@@ -50,7 +68,7 @@ main(int argc, char **argv)
   parser_init(&parser, &lexer);
   ast_function_t func = parser_parse_function(&parser);
 
-  printf("function name='%s' and return type '%d' with value %d\n", func.name, func.return_type, func.body.number);
+  generate_gas_x86_64_linux(&func);
 
   return EXIT_SUCCESS;
 }
-- 
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