added example prorgam which creates and joins threads

programs/Makefile

@@ -8,5 +8,8 @@ simple:
 spawn:
 	$(CC) $(CFLAGS) -o spawn spawn.c
 
-all: simple spawn
+thread:
+	$(CC) $(CFLAGS) -o threads threads.c
+
+all: simple spawn threads
 

programs/threads.c

@@ -0,0 +1,129 @@
+#include "threads.h"
+
+int main()
+{
+    dbgln("main", 4);
+
+    int arg1 = 30;
+    int arg2 = 50;
+    struct optional_int t1 = spawn(thread, &arg1);
+
+    if (has_error(t1)) {
+        __asm__("ebreak");
+        return 1;
+    }
+    struct optional_int t2 = spawn(thread, &arg2);
+    if (has_error(t2)) {
+        __asm__("ebreak");
+        return 2;
+    }
+
+    t1 = join(t1.value, 1000);
+    if (has_error(t1)) {
+        return -1;
+    }
+    t2 = join(t2.value, 1000);
+    if (has_error(t2)) {
+        return -2;
+    }
+
+    dbgln("children exited!", 16);
+
+    return 0;
+}
+
+int thread(void* args)
+{
+    // read value
+    int arg = *((int*) args);
+    //char buff[64] = "sleeping for ";
+    //char* end = itoa(arg, &buff[13], 10);
+
+    // print given number
+    //dbgln(buff, 13);
+
+    sleep(arg);
+
+    // return value as exit code
+    return arg;
+}
+
+/*
+ * Additional functions
+ */
+
+void dbgln(char* text, int len)
+{
+    while (len > TEXT_IO_BUFLEN) {
+        dbgln(text, TEXT_IO_BUFLEN);
+        text += TEXT_IO_BUFLEN;
+        len -= TEXT_IO_BUFLEN;
+    }
+
+    char* ioaddr = (char*) TEXT_IO_ADDR + 4;
+
+    for (int i = 0; i < len; i++) {
+        if (*text == 0)
+            break;
+        *ioaddr++ = *text++;
+    }
+
+    if (len < TEXT_IO_BUFLEN)
+        *ioaddr = '\n';
+
+    // write a 1 to the start of the textIO to signal a buffer flush
+    *((char*) TEXT_IO_ADDR) = 1;
+}
+
+char alpha[16] = "0123456789abcdef";
+char* itoa(int value, char* str, int base)
+{
+    if (base > 16 || base < 2) {
+        *str++ = '?';
+        return str;
+    }
+
+    if (value < 0) {
+        *str++ = '-';
+        value *= -1;
+    }
+
+    int digits = 0;
+    int num = 0;
+
+    // reverse number
+    do {
+        num = num * base;
+        num += value % base;
+        value = value / base;
+        digits++;
+    } while (value > 0);
+
+    value = num;
+    do {
+        num = value % base;
+        value = value / base;
+        *str++ = alpha[num];
+        digits--;
+    }while (digits > 0);
+
+    return str;
+}
+
+void _start()
+{
+    __asm__ __volatile__ (
+          ".option push\n"
+          ".option norelax\n"
+          "            la      gp, _gp\n"
+          ".option pop\n"
+    );
+
+    register int code asm ("s1") = main();
+    __asm__ __volatile__ (
+         "mv     a0, s1\n"
+         "li     a7, 5\n"
+         "ecall\n"
+         "ebreak\n"
+    );
+}