[omniORB] segfault - bug or not?

[baileyk at schneider.com]

An IDL string maps to a C char*.  The assignment of a string to a sequence
or struct member uses the constness of the char* to determine whether a
deep copy must be made.  Your first example lost the const when it assigned
to a param_str, which is just a char*.  Then the sequence thought it was
taking ownership of the string and tried to delete it causing the SEGV.
The second example did not lose the const and so the sequence made its own
deep copy of the string.

I tend to not rely on the const overloading of the assignment operator and
always use CORBA::string_dup() to copy strings into a sequence or struct
member.  The exception to this is if the string is alread a member or held
by a CORBA::String_var.  In these cases the string member or _var objects
take care to make a deep copy.

So your code should look like this to make the deep copy explicit.

   param_seq my_p;
   my_p.length(1);
   param_str one1;
   one1 = "some string";
   my_p[0] = CORBA::string_dup(one1);


Kendall




                                                                                                                                      
                      Johan Cronje                                                                                                    
                      <jcronje at dsp.sun.ac.za>              To:       omniorb-list at omniorb-support.com                                 
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                      support.com                          Subject:  [omniORB] segfault - bug or not?                                 
                                                                                                                                      
                                                                                                                                      
                      10/24/2003 10:43 AM                                                                                             
                                                                                                                                      
                                                                                                                                      




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Good day

I am in the process of writing a corba application, and have encountered an

interesting situation while testing my application. In my idl file I have
the
following:

   typedef string param_str;
   typedef sequence<param_str> param_seq;

Now in my test implementation I have the following to test my application.

   param_seq my_p;
   my_p.length(1);
   param_str one1;
   one1 = "some string";
   my_p[0] = one1;

This generates SIGSEGV as soon as the program finishes and ~param_seq() is
called (it calls some other string sequence destructors and generates the
signal in /lib/libc.so.6 (_int_free to be precise)).

If I change it to

   param_seq my_p;
   my_p.length(1);
   my_p[0] = "some string";

everything is OK. Is this normal? If so, why doesn't my first attempt work?

Note that I am not running it as a CORBA app yet, I am still implementing
my
interface methods and wrote a small test application that only uses the
methods declared in my IDL file. Surely it should work OK?

Thank you and Best Regards
Johan

- --
"There is beauty in simplicity"                        -- Johan Cronje
- ---------------------------------------------------------------
Johan Cronje
Digital Signal Processing / Telecommunications Group
Electrical and Electronic Engineering Department
University of Stellenbosch
http://www.dsp.sun.ac.za/~jcronje
- ---------------------------------------------------------------
GNUPG Key: http://www.dsp.sun.ac.za/~jcronje/jcronje.asc
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