Re: Zero-size array as struct member

Ian Collins <>
Sat, 21 Aug 2010 20:14:27 +1200
On 08/21/10 06:50 PM, Juha Nieminen wrote:

Goran Pusic<> wrote:

On Aug 20, 12:34 pm, Juha Nieminen<nos...@thanks.invalid> wrote:

?? Tiib<> wrote:

In C++ you should use vector<int> instead, it is about as fast.

   In which system, exactly?

   Unfortunately 'new' (and 'delete') is a rather heavy operation with
most C/C++ standard memory allocators, and if you use std::vector in
the place of the struct hack, you will be doing two 'news' instead of
one malloc().

Why? IMO, new and delete are, on the success path, practically
equivalent on many common implementations. Difference is one if on
malloc failure, and new is inlined.

   You are basing your claims on your personal *opinion*? Rather than,
you know, actually testing it in practice?

I say this claim of yours is poorly founded.

   It's quite well founded. For example, take this short piece of code:

     int main()
         std::set<int> someSet;
         for(int i = 0; i< 10000000; ++i) someSet.insert(i);

You are cheating. std::set<int> != std::vector<int> and is in no way an
equivalent to a dynamically allocated array.

Try your test with a vector, before and after reserving space (which is
the more realistic comparison).

Ian Collins

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