The Daily WTF: Curious Perversions in Information Technology

PJH · 2014-11-04 Reply Admin

xaade:
You just have to reserve a value to represent infinity, then create the rules for how it interacts with other values.

The C++ Standard explicitly prohibits integer types from having a representation for infinity.

Dreikin · 2014-11-05 Reply Admin

dkf:

PJH:
-ftemplate-depth=99999

dkf:
Nearly 3 and a half minutes to count to about 10k?

I think you'll find that's about 100k.

Filed under: Off by 10 error

FrostCat · 2014-11-05 Reply Admin

Flagged for pendantry.

dkf · 2014-11-05 Reply Admin

Dreikin:
I think you'll find that's about 100k.

Umm, yeah. Hanzo'd.

Still, it's not like it ought to take very long. 3½ minutes is criminal. What are they doing, using linear searches of a linked list for template matching?

vdeogmer · 2014-11-05 Reply Admin

Foreach loop that runs once?

another_sam · 2014-11-05 Reply Admin

dkf:
3½ minutes is criminal. What are they doing, using linear searches of a linked list for template matching?

They probably assume that programmers aren't doing what you're trying to do here, which is a pretty reasonable assumption. If you try to break the compiler, you get to put up with the results.

Dreikin · 2014-11-06 Reply Admin

FrostCat:
Flagged for pendantry.

:smiley:

Dreikin · 2014-11-06 Reply Admin

dkf:
Umm, yeah. Hanzo'd.
Still, it's not like it ought to take very long. 3½ minutes is criminal. What are they doing, using linear searches of a linked list for template matching?

I wonder if it's something like:

Copy file
Add instantiation of template<i> to source
Delete old file
Re-evaluate new version of file
Find we need template i+1
Set i to i+1
Goto 1.

Gaska · 2014-11-06 Reply Admin

Finally got some time to do some testing.

#include <iostream>

bool isTurtlesHere(int)
{
    return true;
}

template<unsigned short i> // or unsigned char
bool isTurtlesAllTheWayDown()
{
    if (isTurtlesHere(i)) {
        return isTurtlesAllTheWayDown<i+1>();
    } else {
        return false;
    }
}

int main()
{
    if (isTurtlesAllTheWayDown<0>()) {
        std::cout << "Copernicus was wrong";
    } else {
        std::cout << "Copernicus was right";
    }
}

The results are as expected: the code compiles without any warning (g++ -Wall -Wextra), without optimizations it segfaults, with optimizations we get infinite loop. For unsigned char, it takes a fraction of second to compile. For unsigned short, nonoptimized compilation takes 70 seconds, optimized takes 43 seconds. Binary sizes are as follows:

-rwxr-xr-x 1   42112 11-05 18:15 char-nonoptimized.out
-rwxr-xr-x 1    7554 11-05 18:15 char-optimized.out
-rwxr-xr-x 1 8844424 11-05 18:13 short-nonoptimized.out
-rwxr-xr-x 1    7554 11-05 18:14 short-optimized.out

I don't know how, but I was sure I sent this post yesterday... But apparently I didn't. But it got saved in the cumulonimbus and now, on another computer, I still have a complete text I've written. Discourse having useful feature? TRWTF right here.

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