Re: [Man-db-devel] man-db Guix package: preconv segfaults when hard-coded

[Colin Watson]

On Mon, Jan 14, 2019 at 05:04:44PM +0100, Pierre Neidhardt wrote:
> man-db needs to find preconv.  So what we would typically do is patch
> lib/encodings.c to point to preconv in the /gnu/store:

Have you considered sending a patch to add a --with-preconv option to
man-db's configure script?  It already has similar options for most
other bits of groff, so it would seem reasonable.

> Surprisingly, man only displays this on every call:
> 
> --8<---------------cut here---------------start------------->8---
> /gnu/store/6dv1q0s8rlf1ndaqx2qhnkiz9x4840ba-man-db-2.8.3/bin/man: 
> /gnu/store/mpjn4jfx5i8jxblfj538n22hv56rdnhw-groff-minimal-1.22.3/bin/preconv: 
> Segmentation fault
> --8<---------------cut here---------------end--------------->8---
> 
> However, calling
> 
> --8<---------------cut here---------------start------------->8---
> echo "hêlló"  | 
> /gnu/store/mpjn4jfx5i8jxblfj538n22hv56rdnhw-groff-minimal-1.22.3/bin/preconv 
> -e UTF-8
> --8<---------------cut here---------------end--------------->8---
> 
> works.
> 
> It seems that it has something to do with libpipeline, but I'm not sure
> what.
> 
> Is it wrong to create a pipeline with the full path to the executable?

A full path is just fine; it's passed as the first argument to execvp,
which accepts full paths.

Based on the GDB backtrace you posted in the Guix issue, it seems clear
to me that this is a groff bug involving some kind of fixed-size buffer.
If you can't work it out directly from the code, then valgrind should
help to pinpoint it.

-- 
Colin Watson                                       address@hidden