Make DEBUG_printf() a proper function, implementation is port-dependent.
In particular, unix outputs to stderr, to allow to run testsuite against
micropython built with debug output (by redirecting stderr to /dev/null).
diff --git a/py/gc.c b/py/gc.c
index e66a683..8c4bc69 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -10,7 +10,7 @@
#if 0 // print debugging info
#define DEBUG_PRINT (1)
-#define DEBUG_printf(args...) printf(args)
+#define DEBUG_printf DEBUG_printf
#else // don't print debugging info
#define DEBUG_printf(args...) (void)0
#endif
diff --git a/py/malloc.c b/py/malloc.c
index 5699d86..41cf1fd 100644
--- a/py/malloc.c
+++ b/py/malloc.c
@@ -6,7 +6,7 @@
#include "mpconfig.h"
#if 0 // print debugging info
-#define DEBUG_printf(args...) printf(args)
+#define DEBUG_printf DEBUG_printf
#else // don't print debugging info
#define DEBUG_printf(args...) (void)0
#endif
diff --git a/py/misc.h b/py/misc.h
index 065b070..989650c 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -117,4 +117,7 @@
void vstr_vprintf(vstr_t *vstr, const char *fmt, va_list ap);
#endif
+// Debugging helpers
+int DEBUG_printf(const char *fmt, ...);
+
#endif // _INCLUDED_MINILIB_H
diff --git a/py/qstr.c b/py/qstr.c
index e4f0223..a34479c 100644
--- a/py/qstr.c
+++ b/py/qstr.c
@@ -10,8 +10,7 @@
// also probably need to include the length in the string data, to allow null bytes in the string
#if 0 // print debugging info
-#include <stdio.h>
-#define DEBUG_printf(args...) printf(args)
+#define DEBUG_printf DEBUG_printf
#else // don't print debugging info
#define DEBUG_printf(args...) (void)0
#endif
diff --git a/py/runtime.c b/py/runtime.c
index 9d93dbf..9fc0b97 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -23,8 +23,8 @@
#if 0 // print debugging info
#define DEBUG_PRINT (1)
#define WRITE_CODE (1)
-#define DEBUG_printf(args...) printf(args)
-#define DEBUG_OP_printf(args...) printf(args)
+#define DEBUG_printf DEBUG_printf
+#define DEBUG_OP_printf(args...) DEBUG_printf(args)
#else // don't print debugging info
#define DEBUG_printf(args...) (void)0
#define DEBUG_OP_printf(args...) (void)0