support print(int)

runtime/runtime.c

@@ -4,16 +4,35 @@
 #include <stdio.h>
 #include "runtime.h"
 
+#define print(buf, len) write(STDOUT_FILENO, buf, len)
+
 void __go_printstring(string_t *str) {
 	write(STDOUT_FILENO, str->buf, str->len);
 }
 
+void __go_printint(int32_t n) {
+	// Print integer in signed big-endian base-10 notation, for humans to
+	// read.
+	// TODO: don't recurse, but still be compact (and don't divide/mod
+	// more than necessary).
+	if (n < 0) {
+		print("-", 1);
+		n = -n;
+	}
+	int32_t prevdigits = n / 10;
+	if (prevdigits != 0) {
+		__go_printint(prevdigits);
+	}
+	char buf[1] = {(n % 10) + '0'};
+	print(buf, 1);
+}
+
 void __go_printspace() {
-	write(STDOUT_FILENO, " ", 1);
+	print(" ", 1);
 }
 
 void __go_printnl() {
-	write(STDOUT_FILENO, "\n", 1);
+	print("\n", 1);
 }
 
 void go_main() __asm__("main.main");