[Octave-bug-tracker] [bug #47587] virtual function "message (void)" not defined by classes inheriting from "index_exception"

[Markus Mützel]

URL:
  <http://savannah.gnu.org/bugs/?47587>

                 Summary: virtual function "message (void)" not defined by
classes inheriting from "index_exception"
                 Project: GNU Octave
            Submitted by: mmuetzel
            Submitted on: Do 31 Mär 2016 17:02:29 GMT
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Build Failure
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

While looking into patch #8919 (enable visibility attributes for GCC in build
system) and fiddling around with the visibility flags, I came to a point where
the linker threw the error "undefined reference to typeinfo" for the function
"message" in class "index_exception". After following the hints in e.g. [1]
and making it a pure virtual function, other errors were thrown because
"message" was not defined for many classes inheriting from "index_exception".

I fixed this by explicitly defining "message" in the five instances I found
("index_exception_v1.patch").

Another possible approach [1] would be to define the function "message" in
class "index_exception" to give a standard implementation for inheriting
classes ("index_exception_v2.patch").

I do not know which approach is the better one and am going to attach the two
alternative patches as soon as I have the bug number.

[1]
http://stackoverflow.com/questions/307352/g-undefined-reference-to-typeinfo





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