1

Here I'm allocating 10^9 bits:

#include <bitset>
#include <iostream>

const int N = 1000000000;
std::bitset<N> b;

int main()
{
    std::cout << sizeof(b) << std::endl;
}

I get cc1plus.exe: out of memory allocating 268439551 bytes.

But when I do 

#include <bitset>
#include <iostream>

const int N = 1000000000;
int l[N/32];

int main()
{
    std::cout << sizeof(l) << std::endl;
}

The 125000000 bytes (125 MB) are allocated fine. If I change N to a different power of 10 I see both sizeof are the same. I don't even see where the 268439551 byte limit is coming from, since that's 268.4 MB and I have about 4 GB RAM free. Even on a 32 bit system ~200 MB should not be causing a problem, and somehow the byte limit is reached. What's causing the problem here?

Using gcc 4.8.3 on Windows 8.1 with 8 GB RAM.

qwr
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    The compiler runs out of memory for some reason, so it's possibly a bug in the compiler. I would update it; 4.8.3 is more than two years old. – molbdnilo Jan 11 '17 at 09:00
  • Try using ```-ftrack-macro-expansion=0``` compiler option. If it helps, then you are probably affected by https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56746 – Grisha Jan 11 '17 at 10:35
  • @molbdnilo I tried it again with gcc 5.3.0. The compilation takes about 15 seconds longer but I still get the same error. – qwr Jan 11 '17 at 22:02

1 Answers1

1

This seems to be a bug with GCC for c++11: Gcc uses large amounts of memory and processor power with large C++11 bitsets. Compiling with -std=c++98 was a temporary workaround for me.

qwr
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