Hi Tim, At 2025-05-07T14:59:28+0000, Tim Landscheidt wrote: > the man page for glFrustum (and several others; available > for example at > https://manpages.opensuse.org/Leap-16.0/Mesa-libGL-devel/glFrustum.3gl.en.gz > and attached for convenience) signal a "division by zero" > error when producing text output with groff 1.23.0: > > | $ man ./glFrustum.3gl.en.gz > /dev/null > | troff:<standard input>:226: error: division by zero > | troff:<standard input>:272: error: division by zero > | $ [...] > The text output is also mangled: > | as its argument: > | > | ⎣right_left 0 A 0⎦ > | 0 top_bottom B 0 > | 0 0 C D > | 0 0 −1 0 > | > | A=right_left > | > | B=top_bottom > | > | C=−far_val_near_val > | > | D=−farrval_near_val > > The PostScript output looks fine. > > Is this an error in the man page? If so, how can one fix it?
This is (or looks very much like) a bug of long tooth, first reported (as far as I know) against Debian's groff 1.18.1 package, 22 years ago. https://bugs.debian.org/192144 I created a Savannah ticket for it in 2022. https://savannah.gnu.org/bugs/?62298 I have not root-caused this issue. Here are my guesses: 1. There is not a problem with the input document. 2. GNU eqn's degradation process to coarse nroff-mode output is buggy given certain inputs. My long-term plan is to tackle this along with some other devious ideas I have for improving GNU eqn's nroff mode output. But I don't plan to start that work before the groff 1.24.0 release at the earliest. Regards, Branden
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