debug: add DEBUG_BREAKPOINT() macro

core/lib/include/debug.h

@@ -59,6 +59,27 @@ extern "C" {
 #define DEBUG_PRINT(...) printf(__VA_ARGS__)
 #endif
 
+/**
+ * @def DEBUG_BREAKPOINT
+ *
+ * @brief Set a debug breakpoint
+ *
+ * When `DEVELHELP` is enabled, this traps the CPU and allows to debug the
+ * program with e.g. `gdb`.
+ * Without `DEVELHELP` this turns into a no-op.
+ *
+ * @warning     If no Debugger is attached, the CPU might get stuck here
+ *              and consume a lot of power until reset.
+ *
+ * @param val   Breakpoint context for debugger, usually ignored.
+ */
+#ifdef DEVELHELP
+#include "architecture.h"
+#define DEBUG_BREAKPOINT(val)   ARCHITECTURE_BREAKPOINT(val)
+#else
+#define DEBUG_BREAKPOINT(val)   (void)0
+#endif
+
 /**
  * @name Debugging defines
  * @{

sys/include/architecture.h

@@ -33,6 +33,19 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Set a breakpoint
+ * @warning         If no Debugger is attached, the CPU might get stuck here
+ *                  and consume a lot of power until reset.
+ * @param[in] value Context value for debugger, usually ignored.
+ */
+#ifndef ARCHITECTURE_BREAKPOINT
+/* If no breakpoint instruction is defined, busy wait for debugger
+ * to attach and break to ease backtrace
+ */
+#define ARCHITECTURE_BREAKPOINT(value)  do {} while (1)
+#endif
+
 /* Provide doxygen doc centrally, instead of in every architecture_arch.h */
 #ifdef DOXYGEN
 /**