MessageBox "Abnormal program termination" keeps my application running

Question

...kind of. As illustrated by this extremely simplistic example,

very rarely (only once reported so far), it happens that one of my applications crashes this way. I want to terminate it as I normally do when an unspecific exception occurs. My strategy is to (low-level) log the problem, then terminate. The application is part of a subsystem and I want to (re)start it, if any problem is detected. It's built with C++-Builder 6 and runs on Windows (XP...7, also 8). I learned that an abort() most probably caused the error message. The application has a GUI, that's why a message box is shown instead of just making an (unblocking) output to stderr.

And as long as the message box isn't accepted by a user, my application keeps obviously running, for example it handles timers (the lifebeats in the above example increase) or inter-process messages, fully unaware about the problem.

After reading some answers to What is the easiest way to make a C++ program crash? and Difference between raise(SIGABRT) and abort() methods, I tried the following

void mySignalHandler(int sig)
{
    // low-level error reporting here
    exit(-1);
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
    signal(SIGABRT, mySignalHandler);
    // some more initialisation here
}

which lets my application terminate properly also if abort() or raise(SIGABRT) is called. (I also wish to prevent Windows from "searching for a solution of the problem".)

Is this (registering a signal handler for abort and calling exit there) reliable from your point of view? ...or at least something one can build upon?

Answer 1

In the C++Builder installation folder, check the following files:

• source\cpprtl\Source\misc\errormsg.c - implementation of _ErrorMessage
• source\cpprtl\Source\procses\abort.c - implementation of abort, which calls _ErrorMessage
• source\cpprtl\Source\misc\assert.c - implementation of _assert, which calls _ErrorMessage

errormsg.c defines an undocumented _messagefunc function pointer that you can set to override the default behavior. Although it's undocumented and not declared in any header files, you can declare it as an extern and access it that way. Sample usage:

extern int (_RTLENTRY * _EXPDATA _messagefunc)(char *msg);

static int LogAndDie(char *msg)
{
  LogMessageToSomeFile(msg);
  exit(1);
  return 0;
}

void InitializeErrorHandling()
{
  _messagefunc = LogAndDie;
}