Internals: Implement a continuable IM_DEBUG_BREAK on GCC for common a…

…rchs. (ocornut#2673)

imgui_internal.h

@@ -253,12 +253,19 @@ namespace ImStb
 #endif
 
 // Debug Tools
-// Use 'Metrics->Tools->Item Picker' to break into the call-stack of a specific item.
+// Use 'Metrics/Debugger->Tools->Item Picker' to break into the call-stack of a specific item.
+// This will call IM_DEBUG_BREAK() which you may redefine yourself. See https://github.com/scottt/debugbreak for more reference.
 #ifndef IM_DEBUG_BREAK
-#if defined(__clang__)
-#define IM_DEBUG_BREAK()    __builtin_debugtrap()
-#elif defined (_MSC_VER)
+#if defined (_MSC_VER)
 #define IM_DEBUG_BREAK()    __debugbreak()
+#elif defined(__clang__)
+#define IM_DEBUG_BREAK()    __builtin_debugtrap()
+#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+#define IM_DEBUG_BREAK()    __asm__ volatile("int $0x03")
+#elif defined(__GNUC__) && defined(__thumb__)
+#define IM_DEBUG_BREAK()    __asm__ volatile(".inst 0xde01")
+#elif defined(__GNUC__) defined(__arm__) && !defined(__thumb__)
+#define IM_DEBUG_BREAK()    __asm__ volatile(".inst 0xe7f001f0");
 #else
 #define IM_DEBUG_BREAK()    IM_ASSERT(0)    // It is expected that you define IM_DEBUG_BREAK() into something that will break nicely in a debugger!
 #endif