Void Linux with musl error cc: tcc: error: undefined symbol '__atomic_thread_fence'

[robotamer]

Describe the bug

I have upgraded V after a few months of inactivity.
Now I am getting this error

      cc: tcc: error: undefined symbol '__atomic_thread_fence'

I can compile simple code such as hello world etc.
But anything more complex such as vpm, ved ... gives me this error.

musl-dev is installed !!!

    [*] musl-devel-1.2.5_2 Musl C library - development files

I am not sure if this was working before the upgrade. I was only learning V, hence doing simple stuff.
I am now ready to deep dive in to V, but need this to work first.

Reproduction Steps

cd ved
v .

Expected Behavior

should_compile: true

Current Behavior

$ v -v outdated                                                                                  
launch_tool vexe        : /home/tamer/code/v/v/v
launch_tool vroot       : /home/tamer/code/v/v
launch_tool tool_source : /home/tamer/code/v/v/cmd/tools/vpm
launch_tool tool_exe    : /home/tamer/code/v/v/cmd/tools/vpm/vpm
launch_tool tool_args   : '-v' 'outdated'
launch_tool should_compile: true
Compiling vpm with: "'/home/tamer/code/v/v/v' '/home/tamer/code/v/v/cmd/tools/vpm'"
cannot compile `/home/tamer/code/v/v/cmd/tools/vpm`: 1
================== C compilation error (from tcc): ==============
cc: tcc: error: undefined symbol '__atomic_thread_fence'
=================================================================
Try passing `-g` when compiling, to see a .v file:line information, that correlates more with the C error.
(Alternatively, pass `-show-c-output`, to print the full C error message).
builder error: 
==================
C error found. It should never happen, when compiling pure V code.
This is a V compiler bug, please report it using `v bug file.v`,
or goto https://github.com/vlang/v/issues/new/choose .
You can also use #help on Discord: https://discord.gg/vlang .

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.5.0 f479e98

Environment details (OS name and version, etc.)

    "os": {
      "name": "Void Linux",
      "vendor": "void"
    },
    "kernel": {
      "release": "6.12.63_1",
      "version": "#1 SMP PREEMPT_DYNAMIC Thu Dec 18 18:36:00 UTC 2025",
      "architecture": "x86_64"
    },
  "bios": {
      "vendor": "AMI",
      "version": "F.64",
      "date": "09/22/2021"
    },
    "cpu": {
      "vendor": "AuthenticAMD",
      "model": "AMD Ryzen 3 3200U with Radeon Vega Mobile Gfx",
      "speed": 2600,
      "cache": 512,
      "cpus": 1,
      "cores": 2,
      "threads": 4
    },
    "memory": {
      "type": "DDR4",
      "speed": 2667,
      "size": 4096
    },

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[tankf33der]

@robotamer Happy Alpine Linux user is here.
Musl fence bug was fixed ~3 weeks ago. Now all works.

show me output from these 3 commands:

which v
v --version
v list

[robotamer]

There we go:

    ~/c/v/ved►which v                                                                                              244.131s (master) 18:28
    /usr/local/bin/v
    ~/c/v/ved►v --version                                                                                                   (master) 18:28
    V 0.5.0 f479e98
    ~/c/v/ved►v list                                                                                                        (master) 18:28
    cannot compile `/home/tamer/code/v/v/cmd/tools/vpm`: 1
    ================== C compilation error (from tcc): ==============
    cc: tcc: error: undefined symbol '__atomic_thread_fence'
    =================================================================
    Try passing `-g` when compiling, to see a .v file:line information, that correlates more with the C error.
    (Alternatively, pass `-show-c-output`, to print the full C error message).
    builder error: 
    ==================
    C error found. It should never happen, when compiling pure V code.
    This is a V compiler bug, please report it using `v bug file.v`,
    or goto https://github.com/vlang/v/issues/new/choose .
    You can also use #help on Discord: https://discord.gg/vlang .
    
    ~/c/v/ved[1]►v -v list                                                                                          42.107s (master) 18:29
    launch_tool vexe        : /home/tamer/code/v/v/v
    launch_tool vroot       : /home/tamer/code/v/v
    launch_tool tool_source : /home/tamer/code/v/v/cmd/tools/vpm
    launch_tool tool_exe    : /home/tamer/code/v/v/cmd/tools/vpm/vpm
    launch_tool tool_args   : '-v' 'list'
    launch_tool should_compile: true
    Compiling vpm with: "'/home/tamer/code/v/v/v' '/home/tamer/code/v/v/cmd/tools/vpm'"
    cannot compile `/home/tamer/code/v/v/cmd/tools/vpm`: 1
    ================== C compilation error (from tcc): ==============
    cc: tcc: error: undefined symbol '__atomic_thread_fence'
    =================================================================
    Try passing `-g` when compiling, to see a .v file:line information, that correlates more with the C error.
    (Alternatively, pass `-show-c-output`, to print the full C error message).
    builder error: 
    ==================
    C error found. It should never happen, when compiling pure V code.
    This is a V compiler bug, please report it using `v bug file.v`,
    or goto https://github.com/vlang/v/issues/new/choose .
    You can also use #help on Discord: https://discord.gg/vlang .
    
    ~/c/v/ved[1]► 

[JalonSolov]

Not bad... 25 commits behind current, but that's just since yesterday.

Definitely needs to be researched.

[tankf33der]

@robotamer I've installed void and I was able to reproduce the problem

[tankf33der]

both if's are false on voidlinux

@[if linux]
fn detect_musl(mut res Preferences) {
	res.is_glibc = true
	res.is_musl = false
	if os.exists('/etc/alpine-release') {
		res.is_musl = true
		res.is_glibc = false
		return
	}
	my_libs := os.walk_ext('/proc/self/map_files/', '').map(os.real_path(it))
	if my_libs.any(it.contains('musl')) {
		res.is_musl = true
		res.is_glibc = false
	}
}

[JalonSolov]

musl just makes it incredibly hard to tell it that's what you've got. There is no help from it to make the determination. Guess we need a 3rd way to check for VoidLinux... :-\

[tankf33der]

import os

fn main() {
	r := os.execute('getconf GNU_LIBC_VERSION').exit_code
	if r > 0 { 
		println('not glibc')
	}
}

[tankf33der]

More advanced version Nr2:

import os

fn main() {
	if os.execute('getconf GNU_LIBC_VERSION').exit_code == 0
		&& os.execute('ldd --version | grep -qi musl').exit_code != 0 {
		println('glibc')
	} else {
		println('musl')
	}
}

[robotamer]

VERSION

@tankf33der

On void musl I get nothing for GNU or LIBC, just following for VERSION

  getconf -a | grep VERSION                                                                                          
  POSIX2_VERSION = 200809
  _POSIX_VERSION = 200809

However it seams this is going to be an easy fix. How about checking with ldd? See output below.

  $ ldd --version                                                                                                   
  musl libc (x86_64)
  Version 1.2.5

[robotamer]

I like this one even better @tankf33der

  ldd /usr/local/bin/v     
  	/lib/ld-musl-x86_64.so.1 (0x7fbda51fa000)
  	libc.so => /lib/ld-musl-x86_64.so.1 (0x7fbda51fa000)

[JalonSolov]

That would reduce the checks down to 2...

@[if linux]
fn detect_musl(mut res pref.Preferences) {
        res.is_glibc = true
        res.is_musl = false
        musl := os.execute('ldd --version').output.contains('musl')
        if musl {
                res.is_musl = true
                res.is_glibc = false
        }
}

[JalonSolov]

I like this one even better @tankf33der

  ldd /usr/local/bin/v     
  	/lib/ld-musl-x86_64.so.1 (0x7fbda51fa000)
  	libc.so => /lib/ld-musl-x86_64.so.1 (0x7fbda51fa000)

That would only work if they had already run v symlink.