Bug 2289 – Stack overflow on very large BigInt to string.

import std.stdio, std.bigint; void main() { auto result = factorial(10_000); writefln(stderr, "Calculated 10,000!"); //Works to this point. auto resultString = result.toString; //Generates stack overflow. } BigInt factorial(uint N) { BigInt result = 1; for(uint i = 2; i <= N; i++) { result *= i; } return result; } Seems to happen at ~20k to 25k decimal digits. A fairly minor bug, since it is very unlikely that too many people will run into it. (I only found it because I was testing the speed of std.bigint on very large numbers.) If this can't be fixed easily, maybe just a better error message such as "Error: Too many digits." would be good enough.

Thanks for the report. I could not reproduce the bug, but looked over the implementation of toString and it uses O(N) stack gratuitously. I replaced that implementation, and I'm pretty sure it solves the issue, so I'll preemptively close the bug.

Oh, and I committed that to svn, so you can get and build phobos from dsource if in a hurry.

(In reply to comment #0) > import std.stdio, std.bigint; > > void main() { > auto result = factorial(10_000); > writefln(stderr, "Calculated 10,000!"); //Works to this point. > auto resultString = result.toString; //Generates stack overflow. > } > > BigInt factorial(uint N) { > BigInt result = 1; > for(uint i = 2; i <= N; i++) { > result *= i; > } > return result; > } > > Seems to happen at ~20k to 25k decimal digits. > > A fairly minor bug, since it is very unlikely that too many people will run > into it. (I only found it because I was testing the speed of std.bigint on very > large numbers.) You'll find the speed of std.bigint is pretty awful. But don't worry, it will improve _signficantly_. The version in Tango (work in progress) is 40X faster for small numbers, rising to 100s of times faster as the number of digits increases.

Fixed dmd 2.019