[Interest] QMap and thread-safe.

[André Somers]

Op 24-7-2013 9:29, Mandeep Sandhu schreef:
> On Wed, Jul 24, 2013 at 12:20 PM, André Somers <andre at familiesomers.nl 
> <mailto:andre at familiesomers.nl>> wrote:
>
>     Op 23-7-2013 13:34, Giuseppe D'Angelo schreef:
>     > On 23 July 2013 13:25, Bill Crocker <william.crocker at analog.com
>     <mailto:william.crocker at analog.com>> wrote:
>     >> Hi all:
>     >>
>     >> The QMap class states that all member functons are reentrant, but
>     >> if I populate a map at program start-up (with QStrings, let's
>     say) and I
>     >> do not change its contents from then on... I should be able to
>     treat the
>     >> member function ::contains() and any other member function
>     which does not
>     >> modify the map as thread-safe.
>     >>
>     >> Is true?
>     > Probably yes, although totally undocumented. (There has been some
>     > discussion before the release of 5.0 -- about whether we should make
>     > it official that using only "const" methods on containers makes them
>     > thread safe, but I don't remember the outcome...)
>     >
>     > HTH,
>     Well, if I understood Herb Sutters talk[1] on this correctly, that
>     basically *is* the meaning of const nowadays...
>
>     André
>
>     [1]
>     http://channel9.msdn.com/posts/C-and-Beyond-2012-Herb-Sutter-You-dont-know-blank-and-blank
>
>
> Thanks for sharing this link. It was very informative. (BTW, this 
> applies only to C++11)
It does, but because Qt is supposed to work well with C++11, I think it 
probably applies to all of Qt, no matter if C++11 is actually used or not.
>
> Also, doesn't a "const" (old sense of the word) member function mean - 
> "I'm not going to alter the state of the object" ?
No, it means that you're not going to change the *observable* state of 
the object. If you do things like lazy evaluation, your internals may 
change even though the observable state does not. That's what mutable is 
helping you do.

André

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