In a multibyte locale such as en_GB.UTF-8, the pg command cannot handle files containing a form feed character (ASCII 0x0c) at the start of a line. The program enters an infinite loop. I've traced the problem to the function endline_for_mb in file pg.c. The code assumes that the libc function wcwidth will return a nonnegative value, which is not true for a form feed character. wcwidth returns -1 and the unsigned variable "pos" goes into underflow. I'll attach a patch which tests whether the character is printable before calling wcwidth. If not, it uses instead the width of the constant L'?' which is later used to replace nonprintable characters. I trust that we can assume printability of this constant :-) The patch is against the latest release from kernel.org but it looks like the code hasn't changed since the last version in Gentoo. Reproducible: Always Steps to Reproduce: 1. Select a multibyte locale (tested with en_GB.UTF-8) 2. Create a file with a form feed character (0x0c) at the start of a line. 3. Try to display this file using the pg command. Actual Results: pg command hangs. Expected Results: pg command should display the file :-)
Created attachment 213620 [details, diff] Proposed patch
upstream has taken your patch ... unless this is a critical issue for you, i'd prefer to just wait for the next release ;)
Thanks - next release is fine. I actually used pg by accident, thinking I was on a different Unix box that doesn't have less installed :-)
