Add assert macros to aid in debugging.

Adds libopencm3/cm3/assert.h header that provides assertion check macros
similar to those provided by the standard C library.

Thanks to Nicolas Schodet for help.

include/libopencm3/cm3/assert.h

@@ -0,0 +1,136 @@
+/** @defgroup debugging Debugging
+
+@brief Macros and functions to aid in debugging
+
+@version 1.0.0
+
+@date 25 September 2012
+
+Two preprocessor defines control the behavior of assertion check macros in
+this module. They allow the choice between generated code size and ease of
+debugging.
+
+If NDEBUG is defined, all assertion checks are disabled and macros do not
+generate any code.
+
+If CM3_ASSERT_VERBOSE is defined, information regarding the position of
+assertion checks will be stored in the binary, allowing for more
+informative error messages, but also significantly increased code size. As
+default assertion checks do not use this information it is only useful if
+the application linked with libopencm3 defines its own
+cm3_assert_failed_verbose() implementation.
+
+LGPL License Terms @ref lgpl_license
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2012 Tomaz Solc <tomaz.solc@tablix.org>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**@{*/
+
+#ifndef LIBOPENCM3_CM3_ASSERT_H
+#define LIBOPENCM3_CM3_ASSERT_H
+
+#include <libopencm3/cm3/common.h>
+
+#define CM3_LIKELY(expr) (__builtin_expect (!!(expr), 1))
+
+#ifdef NDEBUG
+# define cm3_assert(expr) do { (void)0; } while(0)
+# define cm3_assert_not_reached() while(1)
+#else
+# ifdef CM3_ASSERT_VERBOSE
+#  define cm3_assert(expr) do { \
+				if(CM3_LIKELY(expr)) { (void)0; } else { \
+					cm3_assert_failed_verbose( \
+						__FILE__, __LINE__, \
+						__func__, #expr); \
+				} \
+			} while(0)
+#  define cm3_assert_not_reached() do { \
+				cm3_assert_failed_verbose( \
+					__FILE__, __LINE__, \
+					__func__, 0); \
+			} while(0)
+# else
+/** @brief Check if assertion is true.
+ *
+ * If NDEBUG macro is defined, this macro generates no code. Otherwise
+ * cm3_assert_failed() or cm3_assert_failed_verbose() is called if assertion
+ * is false.
+ *
+ * The purpose of this macro is to aid in debugging libopencm3 and
+ * applications using it. It can be used for example to check if function
+ * arguments are within expected ranges and stop execution in case an
+ * unexpected state is reached.
+ *
+ * @param expr expression to check */
+#  define cm3_assert(expr) do { \
+				if(CM3_LIKELY(expr)) { (void)0; } else { \
+					cm3_assert_failed(); \
+				} \
+			} while(0)
+/** @brief Check if unreachable code is reached.
+ *
+ * If NDEBUG macro is defined, this macro generates code for an infinite loop.
+ * Otherwise cm3_assert_failed() or cm3_assert_failed_verbose() is called if
+ * the macro is ever reached.
+ *
+ * The purpose of this macro is to aid in debugging libopencm3 and
+ * applications using it. It can be used for example to stop execution if an
+ * unreachable portion of code is reached. */
+#  define cm3_assert_not_reached() do { \
+				cm3_assert_failed(); \
+			} while(0)
+# endif
+#endif
+
+BEGIN_DECLS
+
+/** @brief Called on a failed assertion.
+ *
+ * Halts execution in an infinite loop. This function never returns.
+ *
+ * Defined as a weak symbol, so applications can define their own
+ * implementation. Usually, a custom implementation of this function should
+ * report an error in some way (print a message to a debug console, display,
+ * LED, ...) and halt execution or reboot the device. */
+void cm3_assert_failed(void) __attribute__ ((__noreturn__));
+
+/** @brief Called on a failed assertion with verbose messages enabled.
+ *
+ * Halts execution in an infinite loop. This function never returns.
+ *
+ * Defined as a weak symbol, so applications can define their own
+ * implementation. Usually, a custom implementation of this function should
+ * report an error in some way (print a message to a debug console, display,
+ * LED, ...) and halt execution or reboot the device.
+ *
+ * @param file File name where the failed assertion occurred
+ * @param line Line number where the failed assertion occurred
+ * @param func Name of the function where the failed assertion occurred
+ * @param assert_expr Expression that evaluated to false (can be NULL) */
+void cm3_assert_failed_verbose(const char *file, int line, const char *func,
+		const char *assert_expr) __attribute__ ((__noreturn__));
+
+END_DECLS
+
+#endif
+
+/**@}*/