On Sun, 2018-03-04 at 11:19 +0100, Ben Franksen wrote:
I had a program I was working on lately (darcs) crash with a segmentation fault after I made a seemingly harmless refactoring. The original code was
[...]
So I looked at the bytestring library to see if there was something that could explain the crash. I found that it uses accursedUnutterablePerformIO all over the place.
I renamed it that (from inlinePerformIO) to discourage people outside of the bytestring library from using it! Its use within the bytestring library has been audited multiple times by multiple people. We're really pretty confident at this stage that the way it is used in the library is sound.
The dire warnings accompanying this "function" (including the citation of a number of problem reports against commonly used libraries) made me think that it may be worthwhile to offer an opt- out for users of libraries like bytestring or text. (Note that I am not claiming my particular crash is due to a bug in bytestring, I merely want to exclude the possibility.)
We wrote those warnings for other people. We're well aware of them ourselves! Duncan