Elvish crashes in Emacs terminal mode

[glycerine]

linux/amd64/ubuntu12.04
version:
"commit 0c77f30
Author: Cheer Xiao xiaqqaix@gmail.com
Date: Tue Dec 9 14:40:04 2014 +0100

Pipes are no longer statically typed.

"

jaten@c03:$ go get -u -t -v github.com/elves/elvish
github.com/elves/elvish (download)
jaten@c03:~$ elvish
panic: runtime error: invalid memory address or nil pointer dereference
    panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4592ec]

goroutine 16 [running]:
runtime.panic(0x5302e0, 0x80d6b3)
    /home/jaten/pkg/go1.3.1/go/src/pkg/runtime/panic.c:279 +0xf5
github.com/elves/elvish/edit.(*writer).commitBuffer(0xc208000320, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:216 +0x6c
github.com/elves/elvish/edit.(*writer).refresh(0xc208000320, 0xc20808a040, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:538 +0x1cd4
github.com/elves/elvish/edit.(*Editor).refresh(0xc20808a000, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/editor.go:121 +0x21b
github.com/elves/elvish/edit.(*Editor).finishReadLine(0xc20808a000, 0xc2080247e0)
...

[xiaq]

This is weird. I will try to reproduce this on Ubuntu 12.04.

[xiaq]

I tried building elvish on Ubuntu 12.04 with go 1.4.1 and could not reproduce the issue. Could you try again with the latest commit? If there is still a problem, please provide me the version of the go toolchain as well as the terminal you are using; it looks like a terminal-related problem.

[glycerine]

still there, crashing at writer.go:216

go1.3.3
ubuntu12.04/amd64
terminal: I run (gnu) screen, then inside screen I run "emacs -nw", then I start a shell with "M-x shell"
It does seem to be related to running inside emacs. If I start elvish just inside screen, it starts up without problem.

:~$ elvish
panic: runtime error: invalid memory address or nil pointer dereference
    panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4d4b5c]

goroutine 16 [running]:
runtime.panic(0x5cb700, 0x8cd613)
    /home/jaten/pkg/go/src/pkg/runtime/panic.c:279 +0xf5
github.com/elves/elvish/edit.(*writer).commitBuffer(0xc2080003e0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:216 +0x6c
github.com/elves/elvish/edit.(*writer).refresh(0xc2080003e0, 0xc208096040, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:538 +0x1cd4
github.com/elves/elvish/edit.(*Editor).refresh(0xc208096000, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/editor.go:121 +0x21b
github.com/elves/elvish/edit.(*Editor).finishReadLine(0xc208096000, 0xc2080247b0)
    /home/jaten/go/src/github.com/elves/elvish/edit/editor.go:298 +0x1bd
runtime.panic(0x5cb700, 0x8cd613)
    /home/jaten/pkg/go/src/pkg/runtime/panic.c:248 +0x18d
github.com/elves/elvish/edit.(*writer).commitBuffer(0xc2080003e0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:216 +0x6c
github.com/elves/elvish/edit.(*writer).refresh(0xc2080003e0, 0xc208096040, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/writer.go:538 +0x1cd4
github.com/elves/elvish/edit.(*Editor).refresh(0xc208096000, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/editor.go:121 +0x21b
github.com/elves/elvish/edit.(*Editor).ReadLine(0xc208096000, 0x631250, 0x7f5207c97e10, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/jaten/go/src/github.com/elves/elvish/edit/editor.go:328 +0x1e1
main.interact()
    /home/jaten/go/src/github.com/elves/elvish/main.go:66 +0x389
main.main()
    /home/jaten/go/src/github.com/elves/elvish/main.go:133 +0x2c

[xiaq]

Thanks. Now I can reproduce that. I'll look into it some time.

The editor part of Elvish makes quite some assumptions about the terminal so it's no surprise that it panics when run in an exotic terminal. It should be programmed more defensively though.

[xiaq]

The Emacs pseudo-tty has really limited capability. For one thing, it does not implement the TIOCGWINSZ ioctl call properly, which is used is query the window size. Instead of the actual window size it always indicates a width of 0 and a height of 0.

I fixed the code so that it will now no longer panic. But Elvish still will not function properly (e.g. you will see some garbage characters) since the line editor relies on the availability of the more advanced terminal capabilities. Actually the line editor of Elvish in its currently form is essentially a full-screen application comparable to Vim.

I might add some "fallback mode" to the line editor at some time in future.

[xiaq]

For further discussion, see #41.