feat: Includes are relative to input file

compiler/src/main.c

@@ -10,6 +10,8 @@
 
 #define EXIT_ARGS_ERROR (3)
 
+const char* input_filename = NULL;
+
 extern FILE* yyin;
 extern int yyparse(void);
 extern int yydebug;
@@ -58,6 +60,7 @@ int main(int argc, char** argv) {
 	if (!input) {
 		panic("fopen");
 	}
+    input_filename = argv[optind];
 
 	if (!output) {
 		output = fopen("m.gen.bf", "w+");

compiler/src/preprocessor.c

@@ -2,6 +2,7 @@
 #include <string.h>
 #include <stdbool.h>
 #include <alloca.h>
+#include <libgen.h>
 
 #include "y.tab.h"
 
@@ -18,6 +19,8 @@ int yylex(void);
 extern char* yytext;
 extern YYSTYPE yylval;
 
+extern const char* input_filename;
+
 static void handle_include(void) {
     int token = yylex();
 
@@ -26,12 +29,30 @@ static void handle_include(void) {
         panic("preprocessor syntax error");
     }
 
-    const char* filename = yylval.str;
+    char* input = strdup(input_filename);
+    char* relative_path = strdup(dirname(input));
+    free(input);
+
+    char* filename = strdup(yylval.str);
+
+    if (filename[0] != '/') {
+        strbuf_t buffer = strbuf_from(relative_path);
+        strbuf_append_c(buffer, '/');
+        strbuf_append(buffer, filename);
+        free(filename);
+        filename = strdup(buffer);
+        strbuf_free(buffer);
+    }
+
+    free(relative_path);
+
     FILE* file = fopen(filename, "r");
     if (file == NULL) {
         panic("file not found");
     }
 
+    free(filename);
+
     push_file_to_yy_stack(file);
 }