Re: basic_string - once more...

[Stefan Olsson <stefan at noname4us dot com>]

Hi!

The issue that i refer to was discussed in detail starting (I think...) with http://gcc.gnu.org/ml/libstdc++/2001-07/msg00004.html

I am well aware that one should use reserve() as the main tool to avoid this problem, but when for instance inserting into a map<string,string> one would still end up with strings that have capacity == length in the current implementation, greatly increasing memory fragmentation (at least in our specfic application which builds strings based on data from a SQL database).

The worst case (not real life, but anyway) example would be:
#include <string>

using namespace std;

int main()
{
        string s;
        int i;

        for( i=0; i<1000000; i++ )
        {
                s+="a";
        }
}

This code will effectively generate "i" number of malloc calls with the current STL and what I am looking for is a way of getting the STL to allocate in X sized chunks (where X would be configurable and in our case probably 8 or 16 bytes) as the GCC 2.95 did.

Thanks!

/Stefan

Paolo Carlini wrote:

Stefan Olsson wrote:

> If it was posted to the list, please give me some pointer to it
> because i can't find anything else than the reserve() bug discussion
> and this is a allocation issue.
>
> Thanks!
>
> /Stefan

Hi Stefan, it's Paolo here, in fact I'm not sure either that the bug I
have just fixed has really to do with your own problem.

I would be happy to work with you toward a solution of your problem but,
*please* summarize it here once more, with a concise description and a
couple of testcases (I must add that if it is in fact an eminently
memory allocation problem Loren Rittle in probably the best person to
take care of it).

Cheers,
Paolo.

-- 
Military intelligence is a contradiction in terms.