HostFS: Fix behavior of realpath() on Windows. Clear carry flag on re…

…turn from hostfs ACPTR (commanderx16#479)

* Windows needs an additional check for resolved path to indicate that a file does not exist

* fix sequential read problems from BASIC, generalize realpath() for Windows

* fix Windows realpath function to handle non-NULL second arg properly

src/ieee.c

@@ -28,8 +28,6 @@
 #include "glue.h"
 #ifdef __MINGW32__
 #include <direct.h>
-// realpath doesn't exist on Windows, but _fullpath is similar enough
-#define realpath(N,R) _fullpath((R),(N),PATH_MAX)
 // Windows just has to be different
 #define localtime_r(S,D) !localtime_s(D,S)
 #endif
@@ -79,6 +77,22 @@ typedef struct {
 
 channel_t channels[16];
 
+#ifdef __MINGW32__
+// realpath doesn't exist on Windows. This function implements its behavior.
+static char *
+realpath(const char *path, char *resolved_path) {
+	char *ret = _fullpath(resolved_path, path, PATH_MAX);
+
+	if (ret && _access(ret,0) && errno == ENOENT) {
+		if (resolved_path == NULL)
+			free(ret);
+		return NULL;
+	}
+
+	return ret;
+}
+#endif
+
 // Prototypes for some of the static functions
 
 static void clear_error();

src/main.c

@@ -1127,7 +1127,7 @@ handle_ieee_intercept()
 			break;
 		case 0xFFA5:
 			s=ACPTR(&a);
-			status = (status & ~2) | (!a << 1);
+			status = (status & ~3) | (!a << 1); // unconditional CLC, and set zero flag based on byte read
 			break;
 		case 0xFFA8:
 			s=CIOUT(a);