LuajitError: builtin/box/console.lua:557: attempt to index local 'buf' (a string value)

[olegrok]

tarantool --version
Tarantool Enterprise For Mac 2.3.0-331-g4d3b2e684
Target: Darwin-x86_64-RelWithDebInfo
Build options: cmake . -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_BACKTRACE=ON
Compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
C_FLAGS: -Wno-unknown-pragmas -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -msse2 -std=c11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts
CXX_FLAGS: -Wno-unknown-pragmas -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -msse2 -std=c++11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts

tarantool> x = {}
---
...

tarantool> x.a = 'hello'
---
...

tarantool> debug.setmetatable(x.a, {__call = function() return 'good bye' end})
---
- true
...

tarantool> x.a
LuajitError: builtin/box/console.lua:557: attempt to index local 'buf' (a string value)
fatal error, exiting the event loop

[cyrillos]

This looks very similar to #4154

[olegrok]

This looks very similar to #4154

I'm not sure because in #4154 the main problem is manipulation with global system functions/tables that are used in console module.

In the current issue I don't affect any system things. All my actions are in "user-space"

[cyrillos]

yup, but the symptoms are quite alike. surely I do not close this bug, still investigating

[olegrok]

There is also #4617

It's fact users can break the console with strange manipulations)

[cyrillos]

yes, all these bugs are in my todo list

[Mons]

Metatables on a string (and also numbers and nils) are shared and they implement interface of string module.

tarantool> debug.getmetatable("").__index == require 'string'
---
- true
...

tarantool> debug.getmetatable("a") == debug.getmetatable("b")
---
- true
...

You CAN'T set metatable to anything arbitrary and expect, that everything will continue to work

users can break the console

This manipulation breaks not console but the whole tarantool runtime

[igormunkin]

@Mons, thanks a lot for your detailed explanation. In addition to it I can only cite Lua Reference Manual:

Tables and full userdata have individual metatables (although multiple tables and userdata can share their metatables). Values of all other types share one single metatable per type; that is, there is one single metatable for all numbers, one for all strings, etc.

Closing with wontfix due to luajit misuse.

[olegrok]

@igormunkin @Mons Thanks!