Android: Report ERROR() with a message box

include/vm.h

@@ -129,8 +129,13 @@ void vm_stack_trace(void);
 _Noreturn void _vm_error(const char *fmt, ...);
 _Noreturn void vm_exit(int code);
 
+#ifdef __ANDROID__
+// Report the error with a message box and exit.
+#define VM_ERROR ERROR
+#else
 #define VM_ERROR(fmt, ...) \
 	_vm_error("*ERROR*(%s:%s:%d): " fmt "\n", __FILE__, __func__, __LINE__, ##__VA_ARGS__)
+#endif
 
 #ifdef VM_PRIVATE
 #include "little_endian.h"

src/system4.c

@@ -401,11 +401,22 @@ static void windows_error_handler(const char *msg)
 }
 #endif
 
+#ifdef __ANDROID__
+static void android_error_handler(const char *msg)
+{
+	SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "xsystem4", msg, NULL);
+}
+#endif
+
 int main(int argc, char *argv[])
 {
 #ifdef _WIN32
 	sys_error_handler = windows_error_handler;
 #endif
+#ifdef __ANDROID__
+	sys_error_handler = android_error_handler;
+#endif
+
 	initialize_instructions();
 	char *ainfile;
 	int err = AIN_SUCCESS;