Added secondary linker config for C64 overlays (incl. demo program).

git-svn-id: svn://svn.cc65.org/cc65/trunk@5679 b7a2c559-68d2-44c3-8de9-860c34a00d81

samples/Makefile

@@ -122,6 +122,9 @@ endif
 
 nachtm:		nachtm.o
 
+overlaydemo:	overlaydemo.o
+	@$(LD) -t $(SYS) -m $(basename $@).map -C $(SYS)-overlay.cfg -o $@ $^ $(CLIB)
+
 plasma:		plasma.o
 
 sieve:		sieve.o

samples/overlaydemo.c

@@ -0,0 +1,86 @@
+/*
+ * Minimalistic overlay demo program.
+ *
+ * 2009-10-02, Oliver Schmidt (ol.sc@web.de)
+ *
+ */
+
+
+
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+
+extern void _OVERLAY1_LOAD__, _OVERLAY1_SIZE__;
+extern void _OVERLAY2_LOAD__, _OVERLAY2_SIZE__;
+extern void _OVERLAY3_LOAD__, _OVERLAY3_SIZE__;
+
+
+void log (char *msg)
+{
+    printf ("Log: %s\n", msg);
+}
+
+
+#pragma code-name (push, "OVERLAY1");
+
+void foo (void)
+{
+    log ("Calling main from overlay 1");
+}
+
+#pragma code-name (pop);
+
+
+#pragma code-name (push, "OVERLAY2");
+
+void bar (void)
+{
+    log ("Calling main from overlay 2");
+}
+
+#pragma code-name (pop);
+
+
+#pragma code-name (push, "OVERLAY3");
+
+void foobar (void)
+{
+    log ("Calling main from overlay 3");
+}
+
+#pragma code-name(pop);
+
+
+unsigned char loadfile (char *name, void *addr, void *size)
+{
+    int file = open (name, O_RDONLY);
+    if (file == -1) {
+        log ("Opening overlay file failed");
+        return 0;
+    }
+
+    read (file, addr, (unsigned) size);
+    close (file);
+    return 1;
+}
+
+
+void main (void)
+{
+    log ("Calling overlay 1 from main");
+    if (loadfile ("overlaydemo.1", &_OVERLAY1_LOAD__, &_OVERLAY1_SIZE__)) {
+        foo ();
+    }
+
+    log ("Calling overlay 2 from main");
+    if (loadfile ("overlaydemo.2", &_OVERLAY2_LOAD__, &_OVERLAY2_SIZE__)) {
+        bar ();
+    }
+
+    log ("Calling overlay 3 from main");
+    if (loadfile ("overlaydemo.3", &_OVERLAY3_LOAD__, &_OVERLAY3_SIZE__)) {
+        foobar ();
+    }
+}