Sensor CXX performance

[guwirth]

@MarcoWagner: i also have a wxWidgets based project with interesting stats.

~150k LoC
INFO: Sensor CXX [cxx] (done) | time=5.475.497ms

[guwirth]

Hi @MarcoWagner,

maybe you can turn on debug info and isolate the problem:

• due to a single cpp file?
• many include files / every cpp file slow?
• A<B<C...; slow #2131?
• ....

Regards,

[MarcoWagner]

its #2131

[guwirth]

Hi @MarcoWagner,

could you provide a sample please?

Regards,

[MarcoWagner]

#include <iostream>
#include <string>
#include <sstream>

std::ostream& operator< (std::ostream& dest, const std::string& what) { 
   return dest;
}

int main () 
{
   std::string a, b, c, d, e, f;
   std::stringstream dest;
   
   dest < a < b < c < d < e < f;
}

Seems to be O(n!)

That this code is inside a wxWidgets project is just a coincidence

[guwirth]

Hi @MarcoWagner,

I’m wondering why someone creates an own streaming operator with <? Why not writing <<?

The problem is in the grammar where has to be decided if something like this is a conditional expression or a cascaded template. This construct leads to a lot of backtracking and slow speed. Found up to now no solution to speed that up. The case where something like this ends up in a template is more likely and fast.

Ideas are welcome.

Regards,

[MarcoWagner]

I also don't like that operator< and operator> "missuse". cppcheck is also detecting it as an suspicous operator usage und does sometimes alert it as uninitialized variable usage.... But that discussion is out of scope. ;-)

Maybe the parser can detect this construct, warn and skip over?

[guwirth]

duplicate #2131