Double free error when requiring vips in Busted tests

[scossu]

When running Busted tests, if vips is required by more than one test file, the program crashes during garbage collection.

Arch Linux, Lua 5.4.8, lua-vips 1.1-12, busted 2.2.0-1.

Minimally reproducible example:

1. Create two identical files, test1.lua and test2.lua, with the following content:

local vips = require "vips"
describe("Test", function() end)

2. Run busted test1.lua test2.lua
3. Lua crashes during garbage collection with the message: free(): double free detected in tcache 2.

I am unfamiliar with the way busted parses and runs the files, so I wasn't able to determine what exactly is causing the crash.

[scossu]

This may or may not be related to #101 given the same environment and the garbage collector involved.

[rolandlo]

Thanks a lot for reporting. The issue appears also with Lua 5.2 and Lua 5.3 although with slightly different error messages.

With Lua 5.2:

✱
0 successes / 0 failures / 1 error / 0 pending : 0.043979 seconds

Error → /usr/local/lib/luarocks/rocks-5.2/busted/2.2.0-1/bin/busted @ 3
suite test2.lua
/usr/local/lib/luarocks/rocks-5.2/busted/2.2.0-1/bin/busted:3: error in __gc metamethod (expected cdata for arg #1)
double free or corruption (!prev)
Aborted (core dumped)

With Lua 5.3:

0 successes / 0 failures / 0 errors / 0 pending : 0.048136 seconds
free(): invalid pointer
Aborted (core dumped)

With Lua 5.4 (for the record):

0 successes / 0 failures / 0 errors / 0 pending : 0.045718 seconds
free(): double free detected in tcache 2
Aborted (core dumped)

With Luajit no errors:

0 successes / 0 failures / 0 errors / 0 pending : 0.03097 seconds

[rolandlo]

The issue must lie in luaffi-tkl, since the same problem appears with test file

local ffi = require "ffi"
describe("Test", function() end)

[scossu]

This is not directly caused by vips and a workaround has been suggested in Tekenlight/luaffifb#5. Closing.