AP_HAL: add gtests for snprintf

libraries/AP_HAL/tests/test_vsnprintf.cpp

@@ -0,0 +1,39 @@
+#include <AP_gtest.h>
+#include <AP_HAL/HAL.h>
+#include <AP_HAL/Util.h>
+
+const AP_HAL::HAL& hal = AP_HAL::get_HAL();
+
+#define streq(x, y) (!strcmp(x, y))
+
+// from the GNU snprintf manpage:
+
+       // The functions snprintf() and vsnprintf() do not write  more  than  size
+       // bytes  (including the terminating null byte ('\0')).  If the output was
+       // truncated due to this limit, then the return value  is  the  number  of
+       // characters  (excluding the terminating null byte) which would have been
+       // written to the final string if enough space had been available.   Thus,
+       // a  return  value  of  size or more means that the output was truncated.
+
+TEST(vsnprintf_Test, Basic)
+{
+    char output[300];
+    {
+        int bytes_required = hal.util->snprintf(output, ARRAY_SIZE(output), "Fred: %u", 37);
+        EXPECT_TRUE(streq(output, "Fred: 37"));
+        EXPECT_EQ(bytes_required, 8);
+    }
+    {
+        int bytes_required = hal.util->snprintf(output, 3, "Fred: %u", 37);
+        EXPECT_TRUE(streq(output, "Fr"));
+        EXPECT_EQ(bytes_required, 8);
+    }
+    {
+        snprintf(output, ARRAY_SIZE(output), "0123");
+        int bytes_required = hal.util->snprintf(output, 0, "Fred: %u", 37);
+        EXPECT_TRUE(streq(output, "0123"));
+        EXPECT_EQ(bytes_required, 8);
+    }
+}
+
+AP_GTEST_MAIN()

libraries/AP_HAL/tests/wscript

@@ -0,0 +1,7 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+def build(bld):
+    bld.ap_find_tests(
+        use='ap',
+    )