Hello Ming and all,
I have now done some research into SWIG and exceptions. After reading
the SWIG documentation, I found out that SWIG indeed parses the C++
exception specification to figure out for what types of exceptions
"catch(..)" should be generated (see
http://www.swig.org/Doc3.0/SWIGDocumentation.html#SWIGPlus_exception_specifications
). Exception types that are specified in the exception specification are
automatically propagated to the higher language (Java, C# etc.). Now
that we need to remove the exception specification, we lose that
capability. Thanks to Ming for the hint. However there is the
possibility to adapt the SWIG interface file
("pjsip-apps/src/swig/pjsua2.i") and to add explicit "%catches"
statements for each method that describe which types of exceptions the
method could possibility throw. So I guess I need to rework my patch for
this. I just hope that I will find some way to avoid having to annotate
every method with "%catches".... I'll see. Or if someone knows how to do
it, then I would be very grateful for a reply.
Best regards,
Christian
On 24/09/18 12:43, Christian Hoff wrote:
Hello Ming,
thanks for your reply! I will have a look into the SWIG topic this
evening and will let you know my findings.
Best regards,
Christian
On 24/09/18 09:03, Ming wrote:
Hi Christian,
We apologize for the delay in response. We're currently reviewing it
and have also managed to do some testing. While for C/C++, this seems
to be okay, we're still considering how to best handle this for our
Android and Java (via SWIG binding), which may still need the "throw"
specifications in order for the developers to know that the functions
may throw some exceptions.
If you have any feedback regarding this, please let us know.
Best regards,
Ming
On Mon, Sep 24, 2018 at 2:32 PM Christian Hoff
<christian_hoff@xxxxxxx> wrote:
Hello all,
some feedback for this patch is still appreciated. In general I am
getting somewhat frustrated about the collaboration with people who
want
to contribute to the project. Already in the past other people have
posted patches here to this list, but did not get any response - not
even a response what needs to be changed for the patch to be
accepted. I
think this is not a good mode of collaboration. Everyone who posts a
patch here to this mailing list has done this with the intention to
help
the project PJSIP to move along (and has spent much time developing the
patch), so you should at least return the favour and review the patch.
This particular issue that I am trying to address with my patch (that
the PJSUA2 headers don't compile against C++17) is an issue that you
will eventually need to fix anyhow, so why not fix it right now? As of
now, modern versions of GCC use C++ 14 by default, it is only a matter
of time until C++ 17 will become the default and people will start
complaining that there are compile errors from the PJSUA2 headers.
Besides this, my own app uses PJSUA2 with C++ 17 features, so I would
have to revert back to C++14 if this patch is not accepted upstream.
This would be really unnecessary. So I would really appreciate a patch
review.
Best regards,
Christian
On 18/09/18 20:57, Christian Hoff wrote:
Hello all,
Hello Ming & Riza,
do you have any feedback regarding this patch for C++ 17 support? I am
also willing to rework it if required, but some feedback would be
nice.
Thanks in advance and kind regards,
Christian
On 12/09/18 18:23, Christian Hoff wrote:
Hello all,
currently it is not possible to compile a pjsua2 application with
C++17. The reason is that C++17 removes support for dynamic exception
specifications (that is "throws ..." declarations at the end of a
function). Unfortunately PJSUA2 makes heavy use of exception
specifications and most PJSUA2 functions are declared as "throw
(Error)" - meaning that they can throw an exception of type "Error"
that the programmer is supposed to catch.
The consequence is that a lot of compile errors can be observed when
compiling a pjsua2 application with C++17. The compile errors look as
follows:
/usr/local/include/pjsua2/json.hpp:80:33: error: ISO C++17 does not
allow dynamic exception specifications
virtual string saveString() throw(Error);
^~~~~
The compile of the same application worked fine when using the C++14
standard, but it got broken when I switched from C++14 to the C++17
standard.
See
https://www.bfilipek.com/2017/05/cpp17-details-fixes-deprecation.html#removing-deprecated-exception-specifications-from-c17
and
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0003r0.html
for more background about the removal of exception specifications.
To make the application compile again, I had to remove "throw(Error)"
in the whole PJSUA2 source code and include files. This seems to be
the only viable and good fix for this issue. I wrote my own "sed"
script to do that and made some cosmetic corrections afterwards. Then
I generated the attached patch file. Could you please apply this
patch to the code base or give me feedback what I still need to
improve? I verified that pjsip compiles fine with the patch applied.
Thank you very much!
Best regards,
Christian
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