Add format checking to Stream methods

Author: kjbracey

platform/Stream.h

@@ -20,6 +20,7 @@
 #include "platform/FileLike.h"
 #include "platform/FileHandle.h"
 #include "platform/NonCopyable.h"
+#include "mbed_toolchain.h"
 #include <cstdio>
 #include <cstdarg>
 
@@ -47,10 +48,10 @@ class Stream : public FileLike, private NonCopyable<Stream> {
     int puts(const char *s);
     int getc();
     char *gets(char *s, int size);
-    int printf(const char *format, ...);
-    int scanf(const char *format, ...);
-    int vprintf(const char *format, std::va_list args);
-    int vscanf(const char *format, std::va_list args);
+    int printf(const char *format, ...) MBED_PRINTF_METHOD(1, 2);
+    int scanf(const char *format, ...) MBED_SCANF_METHOD(1, 2);
+    int vprintf(const char *format, std::va_list args) MBED_PRINTF_METHOD(1, 0);
+    int vscanf(const char *format, std::va_list args) MBED_SCANF_METHOD(1, 0);
 
     operator std::FILE *()
     {

platform/mbed_toolchain.h

@@ -356,7 +356,7 @@
 
 #ifndef MBED_PRINTF_METHOD
 #if defined(__GNUC__) || defined(__CC_ARM)
-#define MBED_PRINTF_METHOD(format_idx, first_param_idx) __attribute__ ((__format__(__printf__, format_idx+1, first_param_idx+1)))
+#define MBED_PRINTF_METHOD(format_idx, first_param_idx) __attribute__ ((__format__(__printf__, format_idx+1, first_param_idx == 0 ? 0 : first_param_idx+1)))
 #else
 #define MBED_PRINTF_METHOD(format_idx, first_param_idx)
 #endif
@@ -372,7 +372,7 @@
 
 #ifndef MBED_SCANF_METHOD
 #if defined(__GNUC__) || defined(__CC_ARM)
-#define MBED_SCANF_METHOD(format_idx, first_param_idx) __attribute__ ((__format__(__scanf__, format_idx+1, first_param_idx+1)))
+#define MBED_SCANF_METHOD(format_idx, first_param_idx) __attribute__ ((__format__(__scanf__, format_idx+1, first_param_idx == 0 ? 0 : first_param_idx+1)))
 #else
 #define MBED_SCANF_METHOD(format_idx, first_param_idx)
 #endif