From bc5d07ab2a8493b5b343f9f661d3529e6b33ad2d Mon Sep 17 00:00:00 2001
From: Pavel Kirienko <pavel.kirienko@gmail.com>
Date: Sat, 21 Mar 2015 16:01:16 +0300
Subject: [PATCH] snprintf() fix

---
 libuavcan/include/uavcan/build_config.hpp |  8 +++++
 libuavcan/include/uavcan/std.hpp          | 42 ++++++++++++++++++-----
 2 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/libuavcan/include/uavcan/build_config.hpp b/libuavcan/include/uavcan/build_config.hpp
index eab0e386fe..13a6725f4d 100644
--- a/libuavcan/include/uavcan/build_config.hpp
+++ b/libuavcan/include/uavcan/build_config.hpp
@@ -134,6 +134,14 @@
 # define UAVCAN_IMPLEMENT_PLACEMENT_NEW 0
 #endif
 
+/**
+ * Allows the user's application to provide custom implementation of uavcan::snprintf(),
+ * which is often useful on deeply embedded systems.
+ */
+#ifndef UAVCAN_USE_EXTERNAL_SNPRINTF
+# define UAVCAN_USE_EXTERNAL_SNPRINTF   0
+#endif
+
 /**
  * Run time checks.
  * Resolves to the standard assert() by default.
diff --git a/libuavcan/include/uavcan/std.hpp b/libuavcan/include/uavcan/std.hpp
index 9e1cbc9a84..c04ced0c89 100644
--- a/libuavcan/include/uavcan/std.hpp
+++ b/libuavcan/include/uavcan/std.hpp
@@ -2,11 +2,11 @@
  * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
  */
 
-#ifndef UAVCAN_STDINT_HPP_INCLUDED
-#define UAVCAN_STDINT_HPP_INCLUDED
+#ifndef UAVCAN_STD_HPP_INCLUDED
+#define UAVCAN_STD_HPP_INCLUDED
 
 #include <uavcan/build_config.hpp>
-#include <cstdio>
+#include <cstdarg>
 
 #if !defined(UAVCAN_CPP_VERSION) || !defined(UAVCAN_CPP11)
 # error UAVCAN_CPP_VERSION
@@ -20,8 +20,6 @@
 namespace uavcan
 {
 
-using std::snprintf;   // Can be used to replace standard snprintf() with a user-provided one.
-
 typedef std::uint8_t uint8_t;
 typedef std::uint16_t uint16_t;
 typedef std::uint32_t uint32_t;
@@ -37,13 +35,11 @@ typedef std::int64_t int64_t;
 #else
 
 # include <stdint.h>  // Standard integer types from C library
-# include <stdio.h>   // snprintf() from the C library
+# include <stdio.h>   // vsnprintf() from the C library
 
 namespace uavcan
 {
 
-using ::snprintf;
-
 typedef ::uint8_t uint8_t;
 typedef ::uint16_t uint16_t;
 typedef ::uint32_t uint32_t;
@@ -58,4 +54,32 @@ typedef ::int64_t int64_t;
 
 #endif
 
-#endif // UAVCAN_STDINT_HPP_INCLUDED
+namespace uavcan
+{
+/**
+ * Wrapper over the standard snprintf(). This wrapper is needed because different standards and different
+ * implementations of C++ do not agree whether snprintf() should be defined in std:: or in ::. The solution
+ * is to use 'using namespace std' hack inside the wrapper, so the compiler will be able to pick whatever
+ * definition is available in the standard library. Alternatively, the user's application can provide a
+ * custom implementation of uavcan::snprintf().
+ */
+#if __GNUC__
+__attribute__ ((format(printf, 3, 4)))
+#endif
+extern int snprintf(char* out, std::size_t maxlen, const char* format, ...);
+
+#if !UAVCAN_USE_EXTERNAL_SNPRINTF
+inline int snprintf(char* out, std::size_t maxlen, const char* format, ...)
+{
+    using namespace std;  // This way we can pull vsnprintf() either from std:: or from ::.
+    va_list args;
+    va_start(args, format);
+    const int return_value = vsnprintf(out, maxlen, format, args);
+    va_end(args);
+    return return_value;
+}
+#endif
+
+}
+
+#endif // UAVCAN_STD_HPP_INCLUDED