Re: call for libstdc++ profile mode diagnostic ideas

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 29 December 2010 01:15, Hargett, Matt wrote:
>
> 1) allocation of std::string in local variable
> 2) calls to said local string's c_str() method within loops
> 3) and said loops do not modify the contents of the value returned from c_str()

You can't modify the contents, c_str() returns a const char*

> Example:
>
> #include <string>
> #include <cstdio>
>
> void notify(const char* printable) { printf("%s\n", printable); }
>
> int main(void)
> {
> ?std::string name("bob");
> ?for (int i = 0; i < name.length(); i++)
> ?{
> ? ?notify(name.c_str());

What would you do to improve performance here?
I don't see any significant opportunity for optimisation here.

The second idea is obviously useful, as it could avoid unnecessary
heap allocations (although not in C++0x where strings are not going to
be reference-counted.)