[UIFontDescriptor initialize] may have been in progress in another thread when fork() was called

[erdemgezer]

Having interesting errors both on Mac and Ubuntu (Docker) while adding text on top of an image using ruby-vips.

text = Vips::Image.text(
        text_content,
        width: width,
        height: height,
        align: vips_align,
        font: font_name,
        fontfile: font_file,
        spacing: line_spacing
      )
image.composite(text, :over, x: x, y: y)

On my mac development environment, If I call this method from an ActiveJob, it fails with:

objc[25970]: +[UIFontDescriptor initialize] may have been in progress in another thread when fork() was called.
objc[25970]: +[UIFontDescriptor initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

Using of env var OBJC_DISABLE_INITIALIZE_FORK_SAFETY=yes fixes it as suggested in #155 (comment)

However, on Ubuntu docker environment I randomly get segmentation fault errors or floating point exception errors when running the from Rails console.

Everthing works fine if I don't use the .text method in both environments.

Mac stack
MacOS 15.3.1 (M2)
Ruby 3.3.5
Rails 7.2.1
vips-8.16.0

Ubuntu stack
Dockerized x86_64
Linux 116.202.15.119-1f5530ef76b3 6.8.0-54-generic
Using libvips42 package
Ruby 3.3.5
Rails 7.2.1

[jcupitt]

Hi @erdemgezer,

There have been some improvements to locking in text rendering in recent libvipses. Have you tried your Ubuntu example with current stable libvips (8.16.1)?

Text rendering is extremely complex, unfortunately, and interacts with a huge number of different libraries and system components on the various platforms :(

[erdemgezer]

Hi @erdemgezer,

There have been some improvements to locking in text rendering in recent libvipses. Have you tried your Ubuntu example with current stable libvips (8.16.1)?

Text rendering is extremely complex, unfortunately, and interacts with a huge number of different libraries and system components on the various platforms :(

Hi @jcupitt ,
Thanks for letting me know about the latest stable release. I used to install libvips via apt-get from the Dockerfile but I believe I need to build it from source to be able to use the latest version. I'll give it a go and share the results.

[kleisauke]

@erdemgezer Were you able to make any progress with this?

Linux 116.202.15.119-1f5530ef76b3 6.8.0-54-generic

For triage purposes: this looks like Ubuntu 24.04, which provides libvips 8.15.1.

[erdemgezer]

@kleisauke I've tried building latest libvips 8.16.1 but didn't help with random segmentation fault errors on Ubuntu.

[kleisauke]

Does this only occur if you run it from the Rails console? Can you reproduce this without the fontfile argument? I tried this:

$ docker run -e DEBIAN_FRONTEND=noninteractive -v $(pwd):/src -w /src -it ubuntu:24.04 sh -c "\
    apt-get update -y && \
    apt-get install -y --no-install-recommends libvips-tools && \
    vips text hello_world.png '<span foreground=\"#ff5500\" background=\"#c8c8c8\">Hello, world!</span>' --width 500 --height 500 --dpi 300 --rgba"

Which produces:

So at least that seems to work without any issues.

[erdemgezer]

I think it only occurs when I use the fontfile argument and run from Rails console.
I'll try to reproduce again and let you know asap.

[kleisauke]

Note to self: check if this is related to Rails (or Puma) its fork() behaviour. Perhaps the Pango thread here is spawned before the fork() call?

[erdemgezer]

@kleisauke it's also randomly failing when it's called from a SolidQueue Job (ActiveJob). It usually works on the second retry.

Type | SolidQueue::Processes::ProcessExitError
Process pid=46 exited unexpectedly. Received unhandled signal 8.

[kleisauke]

I might have identified the underlying issue, see PR libvips/libvips#4542.