gtkhello sample does not work on macOS

[izarif]

Terminal output:

lua-5.3: /usr/local/share/lua/5.3/lgi/override/cairo.lua:31: attempt to index a nil value (field '_module')
stack traceback:
	/usr/local/share/lua/5.3/lgi/override/cairo.lua:31: in main chunk
	[C]: in function 'require'
	/usr/local/share/lua/5.3/lgi/namespace.lua:176: in function 'lgi.require'
	/usr/local/share/lua/5.3/lgi/namespace.lua:163: in function 'lgi.require'
	/usr/local/share/lua/5.3/lgi/namespace.lua:163: in function 'lgi.require'
	create-main-window.lua:4: in main chunk
	[C]: in ?

[psychon]

Don't ask me how to get it, but I think this means that you do not have the GObject introspection typelib for cairo.

Can you run lua -e 'print(require("lgi.core").module("cairo", 2))' ? It should output something like userdata: 0x5633a73ef358 libcairo.so.2. I guess in your case the first value will be nil.

@pavouk If the above is correct, I'll leave it to you to fix the code so that a better error message is generated when cairo is not available. Also, I don't know which other overrides might be affected.

[TingPing]

Don't ask me how to get it, but I think this means that you do not have the GObject introspection typelib for cairo.

It is generated at build time of gobject-introspection if cairo and cairo-gobject libraries are found.
At a glance the homebrew formula should work though you may need to manually set some env vars but it wasn't mentioned what build was used.

[speeder]

I am also having this problem, I tried copy-pasting that print line above, this is the result:

"nil /usr/local/Cellar/gobject-introspection/1.50.0/lib/libcairo.2.dylib"

I have no idea what is wrong.

EDIT: I did a "brew list cairo" and this got printed:

"/usr/local/Cellar/cairo/1.14.8/lib/libcairo-gobject.2.dylib"

so I guess there is some path misconfiguration somewhere?

[triaxx]

I obtain the same error on NetBSD:
Lua 5.3.4 Copyright (C) 1994-2017 Lua.org, PUC-Rio
> lgi = require("lgi")
> cairo = lgi.cairo
/usr/pkg/share/lua/5.3/lgi/override/cairo.lua:31: attempt to index a nil value (field '_module')
stack traceback:
/usr/pkg/share/lua/5.3/lgi/override/cairo.lua:31: in main chunk
[C]: in function 'require'
/usr/pkg/share/lua/5.3/lgi/namespace.lua:176: in function 'lgi.namespace.require'
(...tail calls...)
stdin:1: in main chunk
[C]: in ?
> print(require("lgi.core")).module("cairo",2)
table: 0x7f7ff7b12100
stdin:1: attempt to index a nil value
stack traceback:
stdin:1: in main chunk
[C]: in ?

However, typelib for cairo is provided by gobject-introspection:
pkg_info -L gobject-introspection|grep cairo
/usr/pkg/lib/girepository-1.0/cairo-1.0.typelib

I would be very happy to receive any advice to identify the problem.

[psychon]

@ffauberteau Can you try print(require("lgi.core").module("cairo",2)) instead of print(require("lgi.core")).module("cairo",2)? (print around everything, not just the require)

[triaxx]

@psychon You're right, I write a typo. But my first error was correct.
The problem was a building dependency. Now it works.
Thanks

[psychon]

@ffauberteau Could you provide more information about that dependency problem? Could others have the same problem and your solution would work for them as well?

[andrewstarks]

I'm having this same issue with lgi. Can @ffauberteau or anyone else shed a bit of light on what the fix was?

[jorge-jbs]

Same issue here. I'm trying to use this library with the nix package manager and I can't make it work. Help would be appreciated.

[psychon]

@jorge-jbs "Nix" sounds a bit like "Linux" to me, so what does lua -e 'print(require("lgi.core").module("cairo", 2))' say for you? Also, no idea about the correct path for it (debian uses /usr/lib/x86_64-linux-gnu/libcairo.so.2 here), but where is your cairo library & is it called libcairo.so.2?

[jorge-jbs]

@psychon It prints nil libcairo.so.2. Nix is not an usual package manager, cairo is located in /nix/store/mwmwbrnj2qvfcwscqx1fxfzzlhqfp011-cairo-1.14.10/lib/libcairo.so.2. But I don't think Nix is the problem.

[psychon]

@jorge-jbs Hm, so it did not find libcairo.so.2. LGI just uses g_module_open("libcairo.so.2", 0). In this case, it looks to me like the code in there just does dlopen("libcairo.so.2", RTLD_NOW). So all that I can tell you is that the dynamic loader does not find libcairo on your system / that the file is not in its search path.
Code for g_module_open: https://sources.debian.net/src/glib2.0/2.53.4-3/gmodule/gmodule.c/#L595 https://sources.debian.net/src/glib2.0/2.53.4-3/gmodule/gmodule-dl.c/#L98

[psychon]

@jorge-jbs Google found the following and to me it sounds like dlopen doesn't have much of a search path on Nix. You could try running with LD_LIBRARY_PATH=/nix/store/mwmwbrnj2qvfcwscqx1fxfzzlhqfp011-cairo-1.14.10/lib/ I guess, but that's mostly a hack. I don't see why you think that

But I don't think Nix is the problem.

https://nixos.org/nix-dev/2011-December/007412.html
https://nixos.org/nix-dev/2014-August/013822.html

[medranocalvo]

It seems to me that the change in dab172c prevents the library search path from being used: an absolute path is used unconditionally in macOS. I think this commit should be reverted. Instead, users/system administrators should make sure the libraries are available in the library search path. It would be helpful for the error message to include a comment about setting LD_LIBRARY_PATH, or using pkg-config to find out what the library search path is.