OUString is mutable?

Stephan Bergmann sbergman at redhat.com
Mon Oct 1 02:56:43 PDT 2012

On 10/01/2012 11:40 AM, Noel Grandin wrote:
> On 2012-10-01 10:15, Stephan Bergmann wrote:
>> Note that the rtl string functionality had originally been designed,
>> arguably somewhat naively, after java.lang.String.  On the Java
>> platform, immutability of String is an important security measure.
>> While that argument is irrelevant in a C/C++ context, immutability is
>> also an important concept when reasoning about multi-threaded code.
>> Therefore, the distinction between OUString and OUStringBuffer IMO
>> does make sense after all.
> I don't see how the design helps you in a multithreaded context.
> If you share an OUString instance between two threads, either thread
> could assign to it, replacing it's contents, and invalidating what the
> other thread sees.
> So it's really not any safer than using an OUStringBuffer.
> It just gives the illusion of safety.

Ach, I hadn't been sufficiently coffeeinated yet.  My mind had somehow 
been fogged into assuming that

   void f(OUString const & s) {
     // use s here without fear of concurrent modification

was correct---which, of course, it is not.

So, yes, the design of the rtl string functionality is not only somewhat 
naive.  (I faintly remember having written about that before, back in 
OOo times, but that's likely lost.)


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