Hello,

I am trying to assert the fact that a UnicodeException is thrown by the piece of code added in this PR:
https://github.com/dlang/druntime/pull/1696/files

The unittest is in druntime/src/rt/lifetime.d:

unittest
{
    import core.exception : UnicodeException;

    try
    {
        string ret;
        int i = -1;
        ret ~= i;
    }
    catch(UnicodeException e)
    {
        assert(e.msg == "Invalid UTF-8 sequence");
    }
}

However running the tests for druntime fails because the exception is not caught:
****** FAIL release64 rt.lifetime
core.exception.UnicodeException@src/rt/lifetime.d(2031): Invalid UTF-8 sequence

I tried to use the same code as in the unittest above in a regular D source file and the UnicodeException was properly caught there.

Do you know what the problem might be?

Thank you,
Lucia

Linux? Probably another bug.
Try this:
unittest
{
    import core.exception : UnicodeException;
    void f()
    {
        string ret;
        int i = -1;
        ret ~= i;
    }

    try
    {
        f();
    }
    catch(UnicodeException e)
    {
        assert(e.msg == "Invalid UTF-8 sequence");
    }
}

On Thursday, November 24, 2016 13:42:25 Kagamin via Digitalmars-d-learn wrote:
> Linux? Probably another bug.
> Try this:
> unittest
> {
>      import core.exception : UnicodeException;
>      void f()
>      {
>          string ret;
>          int i = -1;
>          ret ~= i;
>      }
>
>      try
>      {
>          f();
>      }
>      catch(UnicodeException e)
>      {
>          assert(e.msg == "Invalid UTF-8 sequence");
>      }
> }

If you're doing that, you might as well use std.exception.assertThrown or collectException. e.g.

assertThrown!UnicodeException(f());

or

assert(collectException!UnicodeException(f()).msg ==
       "Invalid UTF-8 sequence.");

You could also do the same with a lambda to avoid the explicit function.

Regardless, I don't know why the OP is hitting this problem, and unfortunately, I can't test it on my local machine at the moment to try and see what's going on.

- Jonathan M Davis

On Thursday, 24 November 2016 at 13:42:25 UTC, Kagamin wrote:
> Linux? Probably another bug.
> Try this:
> unittest
> {
>     import core.exception : UnicodeException;
>     void f()
>     {
>         string ret;
>         int i = -1;
>         ret ~= i;
>     }
>
>     try
>     {
>         f();
>     }
>     catch(UnicodeException e)
>     {
>         assert(e.msg == "Invalid UTF-8 sequence");
>     }
> }

Both the OP's code and this code gives me a segfault on DMD 2.071.1 on my Mac.

On Thursday, 24 November 2016 at 15:18:40 UTC, Ryan wrote:
> On Thursday, 24 November 2016 at 13:42:25 UTC, Kagamin wrote:
>> Linux? Probably another bug.
>> Try this:
>> unittest
>> {
>>     import core.exception : UnicodeException;
>>     void f()
>>     {
>>         string ret;
>>         int i = -1;
>>         ret ~= i;
>>     }
>>
>>     try
>>     {
>>         f();
>>     }
>>     catch(UnicodeException e)
>>     {
>>         assert(e.msg == "Invalid UTF-8 sequence");
>>     }
>> }
>
> Both the OP's code and this code gives me a segfault on DMD 2.071.1 on my Mac.

The PR this unittest is for fixes the segfault issue.
Check out: https://issues.dlang.org/show_bug.cgi?id=5995

On Thursday, 24 November 2016 at 14:47:32 UTC, Jonathan M Davis wrote:
> On Thursday, November 24, 2016 13:42:25 Kagamin via Digitalmars-d-learn wrote:
>> Linux? Probably another bug.
>> Try this:
>> unittest
>> {
>>      import core.exception : UnicodeException;
>>      void f()
>>      {
>>          string ret;
>>          int i = -1;
>>          ret ~= i;
>>      }
>>
>>      try
>>      {
>>          f();
>>      }
>>      catch(UnicodeException e)
>>      {
>>          assert(e.msg == "Invalid UTF-8 sequence");
>>      }
>> }
>
> If you're doing that, you might as well use std.exception.assertThrown or collectException. e.g.
>
> assertThrown!UnicodeException(f());
>
> or
>
> assert(collectException!UnicodeException(f()).msg ==
>        "Invalid UTF-8 sequence.");
>
> You could also do the same with a lambda to avoid the explicit function.
>
> Regardless, I don't know why the OP is hitting this problem, and unfortunately, I can't test it on my local machine at the moment to try and see what's going on.
>
> - Jonathan M Davis

Thanks Kagamin and Jonathan for your suggestions!

I was able to hack my way around it. In druntime there are other modules which need the exact same thing and have their own assertThrown template:
https://github.com/dlang/druntime/search?utf8=%E2%9C%93&q=assertThrown

So I did the same thing and defined assertThrown in my unittest. Now it works fine:
unittest
{
    import core.exception : UnicodeException;

    static void assertThrown(T : Throwable = Exception, E)(lazy E expr, string msg)
    {
        try
            expr;
        catch (T e) {
            assert(e.msg == msg);
            return;
        }
    }

    static void f()
    {
        string ret;
        int i = -1;
        ret ~= i;
    }

    assertThrown!UnicodeException(f(), "Invalid UTF-8 sequence");
}

It is still unclear why this approach is necessary.

Thanks,
Lucia

On Thursday, November 24, 2016 15:41:12 Lucia Cojocaru via Digitalmars-d- learn wrote:
> I was able to hack my way around it. In druntime there are other modules which need the exact same thing and have their own assertThrown template: https://github.com/dlang/druntime/search?utf8=%E2%9C%93&q=assertThrown
>
> So I did the same thing and defined assertThrown in my unittest.
> Now it works fine:
> unittest
> {
>      import core.exception : UnicodeException;
>
>      static void assertThrown(T : Throwable = Exception, E)(lazy E
> expr, string msg)
>      {
>          try
>              expr;
>          catch (T e) {
>              assert(e.msg == msg);
>              return;
>          }
>      }
>
>      static void f()
>      {
>          string ret;
>          int i = -1;
>          ret ~= i;
>      }
>
>      assertThrown!UnicodeException(f(), "Invalid UTF-8 sequence");
> }
>
> It is still unclear why this approach is necessary.
>
> Thanks,
> Lucia

I would advise against this, because it does not match what std.exception.assertThrown does. It use the message you give as the message in the AssertError that gets thrown on failure. It doesn't assert what the message in the thrown exception is. It doesn't care. It just cares that the right type of exception was thrown. If you want to check the message, collectException is more appropriate (though you should check that it's result is non-null, which my example didn't). Regardless, if you're talking about essentially adding a Phobos function as a private helper in druntime, it's a bad idea to make it operate differently from the one in Phobos. It should either be the same, or it should be named differently.

- Jonathan M Davis