Assert instead of throw

Question

How can I set the error handling to assert instead of throw? I'd like it to debug break without attaching the debugger.

Currently, I'm patching the source, adding __debugbreak() to assertions_impl.h in precondition_fail().

To be a bit more specific.

There are a handful of global error handling functions.

Their behavior is determined by checking flag from a function get_static_error_behaviour(). Currently, there are two constants to determine the behavior: THROW_EXCEPTION and CONTINUE. I'd like to add to it assert.

This is an example that throws an exception (I found it somewhere, something about CCW order):


#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polygon_2.h>
#include <CGAL/Polygon_set_2.h>
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef K::Point_2 CGALPoint;
typedef CGAL::Polygon_2<K> CGALInnerPolygon;
typedef CGAL::Polygon_set_2<K> CGALMultiPolygon;

#include <iostream>

using namespace std;

int main()
{
    CGALInnerPolygon cgalpoly;
    cgalpoly.push_back( CGALPoint( 0, 0 ) );
    cgalpoly.push_back( CGALPoint( 1, 1 ) );
    cgalpoly.push_back( CGALPoint( 1, 0 ) );

    CGALMultiPolygon multipolygon;
    multipolygon.insert( cgalpoly );

    printf( "bye\n" );

    return 0;
}

Something has changed, either the new VS2022 or CGAL, but now it doesn't only print, it also throws an exception and VS breakpoints on the right line.

You should never use `assert` instead of `throw` for error handling. `assert` must only be used for situations that really **are not possible**. — akaAbdullahMateen, Jul 16 '22 at 23:59
Have a look [here](https://softwareengineering.stackexchange.com/questions/15515/when-to-use-assertions-and-when-to-use-exceptions) and [here](https://stackoverflow.com/questions/409794/exception-vs-assert) — Irelia, Jul 17 '22 at 00:05
I don't expect cgal lib to change its behavior from throw to assert. However, I expect a flag that I can set that would enable me to switch and use the latter conveniently. — Zohar Levi, Jul 17 '22 at 00:18
If cgal doesn't provide a flag, then you're out of luck. Since assert and exceptions serve entirely different purposes though, it'd be surprising if any such flag existed. — Stephen Newell, Jul 17 '22 at 00:33
@ZoharLevi `if (some_condition) throw SomeException;` -- What would the `assert()` version of that `throw` statement look like? There is trouble trying to "convert" the `throw` to `assert` by hand (deciding what the assert() will contain), let alone find some sort of macro to do the job. — PaulMcKenzie, Jul 17 '22 at 01:01

score 3 · Accepted Answer · answered Jul 31 '22 at 16:21

The behavior on assertion failure can be controlled, as documented here. If I am reading correctly, you want

#include <CGAL/assertions_behaviour.h>
int main(){
  CGAL::set_error_behaviour(CGAL::ABORT);
}

or if that's not quite what you need, you can use CGAL::set_error_handler to provide your own handler.

Assert instead of throw

1 Answers1