on my system, when watching the file, gv issues very often some errors after modification of the pdf-file and that's annoying.
You're right. I guessed it might be reading a half-rewritten PDF file before the new xref table is written (at the end of the file) and getting confused.
Alas, more systematic tests of this hypothesis refuted it. I changed the watch interval to 10 seconds (default is 1 second), to reduce the odds that the PDF file was being rewritten while gv was reloading it. Even that change didn't help. gv still produced tons of interpreter errors. I guess it doesn't reread the xref table properly, or something like that. Whatever the cause, it's a pain.
xpdf has a -remote option, so a Makefile rule could make the pdf and then tell xpdf to reload it, via the command line. But I've never managed to get -remote to work with xpdf.
So I'm back to the original plan of hacking xpdf to use inotify via the inotify_init(2) and inotify_add_watch(2) syscalls (dnotify looks like a pain to use). My inotify 'hello world' programs aren't yet working so I have a ways to go.
`Not all those who wander are lost.' (J.R.R. Tolkien)