Added static assert macro

Added MBED_STATIC_ASSERT for compile-time assertions, results in
compile-time error if condition is false

The assertion acts as a declaration that can be placed at file scope, in
a code block (except after a label), or as a member of
a C++ class/struct/union.

Unfortunately, there does not exist a backup construct for use in
C class/struct/union contexts. An alternative macro,
MBED_STRUCT_STATIC_ASSERT provides this ability to avoid disabling
static assertions for the majority of mbed-supported C compilers.

TESTS/mbedmicro-mbed/static_assert/main.cpp

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdint.h>
+
+#include "toolchain.h"
+#include "greentea-client/test_env.h"
+#include "unity.h"
+#include "utest.h"
+
+using namespace utest::v1;
+
+void no_test() {}
+
+utest::v1::status_t test_setup(const size_t number_of_cases) {
+    GREENTEA_SETUP(5, "default_auto");
+    return verbose_test_setup_handler(number_of_cases);
+}
+
+Case cases[] = {
+    Case("Compilation test", no_test),
+};
+
+Specification specification(test_setup, cases);
+
+int main() {
+    return !Harness::run(specification);
+}

TESTS/mbedmicro-mbed/static_assert/test_c.c

@@ -0,0 +1,39 @@
+#include "mbed_assert.h"
+#define THE_ANSWER 42
+
+// Tests for static asserts in different contexts
+// multiple asserts are used to garuntee no conflicts occur in generated labels
+
+// Test for static asserts in global context
+MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+        "An int must be larger than char");
+MBED_STATIC_ASSERT(2 + 2 == 4,
+        "Hopefully the universe is mathematically consistent");
+MBED_STATIC_ASSERT(THE_ANSWER == 42,
+        "Said Deep Thought, with infinite majesty and calm");
+
+struct test {
+    int dummy;
+
+    // Test for static asserts in struct context
+    MBED_STRUCT_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+            "An int must be larger than char");
+    MBED_STRUCT_STATIC_ASSERT(2 + 2 == 4,
+            "Hopefully the universe is mathematically consistent");
+    MBED_STRUCT_STATIC_ASSERT(THE_ANSWER == 42,
+            "Said Deep Thought, with infinite majesty and calm");
+};
+
+MBED_STATIC_ASSERT(sizeof(struct test) == sizeof(int),
+        "Static assertions should not change the size of a struct");
+
+void doit_c(void) {
+    // Test for static asserts in function context
+    MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+            "An int must be larger than char");
+    MBED_STATIC_ASSERT(2 + 2 == 4,
+            "Hopefully the universe is mathematically consistent");
+    MBED_STATIC_ASSERT(THE_ANSWER == 42,
+            "Said Deep Thought, with infinite majesty and calm");
+}
+

TESTS/mbedmicro-mbed/static_assert/test_cpp.cpp

@@ -0,0 +1,46 @@
+#include "mbed_assert.h"
+#define THE_ANSWER 42
+
+// Tests for static asserts in different contexts
+// multiple asserts are used to garuntee no conflicts occur in generated labels
+
+// Test for static asserts in global context
+MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+        "An int must be larger than char");
+MBED_STATIC_ASSERT(2 + 2 == 4,
+        "Hopefully the universe is mathematically consistent");
+MBED_STATIC_ASSERT(THE_ANSWER == 42,
+        "Said Deep Thought, with infinite majesty and calm");
+
+struct test {
+    int dummy;
+
+    // Test for static asserts in struct context
+    MBED_STRUCT_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+            "An int must be larger than char");
+    MBED_STRUCT_STATIC_ASSERT(2 + 2 == 4,
+            "Hopefully the universe is mathematically consistent");
+    MBED_STRUCT_STATIC_ASSERT(THE_ANSWER == 42,
+            "Said Deep Thought, with infinite majesty and calm");
+
+    MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+            "An int must be larger than char");
+    MBED_STATIC_ASSERT(2 + 2 == 4,
+            "Hopefully the universe is mathematically consistent");
+    MBED_STATIC_ASSERT(THE_ANSWER == 42,
+            "Said Deep Thought, with infinite majesty and calm");
+};
+
+MBED_STATIC_ASSERT(sizeof(struct test) == sizeof(int),
+        "Static assertions should not change the size of a struct");
+
+void doit_c(void) {
+    // Test for static asserts in function context
+    MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+            "An int must be larger than char");
+    MBED_STATIC_ASSERT(2 + 2 == 4,
+            "Hopefully the universe is mathematically consistent");
+    MBED_STATIC_ASSERT(THE_ANSWER == 42,
+            "Said Deep Thought, with infinite majesty and calm");
+}
+

platform/mbed_assert.h

@@ -49,6 +49,66 @@ do {                                                     \
 } while (0)
 #endif
 
+
+#define _MBED_CONCAT_(a, b) a##b
+#define _MBED_CONCAT(a, b) _MBED_CONCAT_(a, b)
+#define _MBED_ASSERTION _MBED_CONCAT(_MBED_ASSERTION_AT_, __LINE__)
+
+/** MBED_STATIC_ASSERT
+ *  Declare compile-time assertions, results in compile-time error if condition is false
+ *
+ *  The assertion acts as a declaration that can be placed at file scope, in a
+ *  code block (except after a label), or as a member of a C++ class/struct/union.
+ *
+ *  @note
+ *  Use of MBED_STATIC_ASSERT as a member of a struct/union is limited:
+ *  - In C++, MBED_STATIC_ASSERT is valid in class/struct/union scope.
+ *  - In C, MBED_STATIC_ASSERT is not valid in struct/union scope, and
+ *    MBED_STRUCT_STATIC_ASSERT is provided as an alternative that is valid
+ *    in C and C++ class/struct/union scope.
+ *
+ *  @code
+ *  MBED_STATIC_ASSERT(MBED_LIBRARY_VERSION >= 120,
+ *          "The mbed library must be at least version 120");
+ *
+ *  int main() {
+ *      MBED_STATIC_ASSERT(sizeof(int) >= sizeof(char),
+ *              "An int must be larger than a char");
+ *  }
+ *  @endcode
+ */
+#if defined(__cplusplus) && (__cplusplus >= 201103L || __cpp_static_assert >= 200410L)
+#define MBED_STATIC_ASSERT(expr, msg) static_assert(expr, msg)
+#elif !defined(__cplusplus) && __STDC_VERSION__ >= 201112L
+#define MBED_STATIC_ASSERT(expr, msg) _Static_assert(expr, msg)
+#elif defined(__cplusplus) && defined(__GNUC__) && defined(__GXX_EXPERIMENTAL_CXX0X__) \
+    && (__GNUC__*100 + __GNUC_MINOR__) > 403L
+#define MBED_STATIC_ASSERT(expr, msg) __extension__ static_assert(expr, msg)
+#elif !defined(__cplusplus) && defined(__GNUC__) && !defined(__CC_ARM) \
+    && (__GNUC__*100 + __GNUC_MINOR__) > 406L
+#define MBED_STATIC_ASSERT(expr, msg) __extension__ _Static_assert(expr, msg)
+#elif defined(__ICCARM__)
+#define MBED_STATIC_ASSERT(expr, msg) static_assert(expr, msg)
+#else
+#define MBED_STATIC_ASSERT(expr, msg) enum {_MBED_ASSERTION = sizeof(char[(expr) ? 1 : -1])}
+#endif
+
+/** MBED_STRUCT_STATIC_ASSERT
+ *  Declare compile-time assertions, results in compile-time error if condition is false
+ *
+ *  Unlike MBED_STATIC_ASSERT, MBED_STRUCT_STATIC_ASSERT can and must be used
+ *  as a member of a C/C++ class/struct/union.
+ *
+ *  @code
+ *  struct thing {
+ *      MBED_STATIC_ASSERT(2 + 2 == 4,
+ *              "Hopefully the universe is mathematically consistent");
+ *  };
+ *  @endcode
+ */
+#define MBED_STRUCT_STATIC_ASSERT(expr, msg) int : (expr) ? 0 : -1
+
+
 #endif
 
 /** @}*/