Stream: platform development

Topic: Compile a zig-sdl2 platform

Oskar Hahn (Aug 03 2024 at 19:00):

Hi

I am trying to write a zig-platform that uses SDL. I am not able, to get it build for the surgical or the legacy linker.

When I build it for the surgical linker, I first create a libapp.so from an example app and then compile the zig-code with it. I get a dynhost-executable. If I start this executalbe it works. It starts the program with the compiled roc code.

But when I try to to start it with roc run, I get the error:

🔨 Rebuilding platform...
Segmentation fault at address 0x78c5b62c8098
/home/ossi/zig/0.13.0/files/lib/compiler_rt/memcpy.zig:14:9: 0x5a929e0bb258 in memcpy (compiler_rt)
    if (len != 0) {
        ^
Unwind error at address `:0x5a929e0bb258` (error.InvalidCFA), trace may be incomplete

I have no idea, what is going on or how to fix it. Does anybody of you have seen an error like this?

The code is here: https://github.com/ostcar/roc-turtle

To build an run the dynhost run:

zig build preprocess
./platform/dynhost

Brendan Hansknecht (Aug 03 2024 at 22:18):

We've been hitting more issues in general with zig 0.13. noticed that on the branch upgrading llvm and zig. No idea why though

Brendan Hansknecht (Aug 03 2024 at 22:20):

So issues that go away in release fast due to skipping extra checks. Others that stick.

Not havimg a trace makes that really hard to guess. Can you form a debug build of the zig host and see if you get a stack trace.

Oskar Hahn (Aug 04 2024 at 06:20):

The zig version is not the issue. I get the same behavior , when I downgrade the code for zig 0.11.0 and compile it with that zig version.

Here is a branch, that for zig 0.11.0: https://github.com/ostcar/roc-turtle/tree/zig-11

zig version
0.11.0

zig build preprocess

./platform/dynhost  # this works

roc build examples/roc/main.roc  # this works

./examples/roc/main
Segmentation fault at address 0x74800dd69098
/home/ossi/zig/0.11.0/files/lib/compiler_rt/memcpy.zig:14:9: 0x5918d42d06d8 in memcpy (compiler_rt)
    if (len != 0) {
        ^
Unwind error at address `:0x5918d42d06d8` (error.InvalidCFA), trace may be incomplete

Oskar Hahn (Aug 04 2024 at 07:00):

I don't know how to create a better stack trace. I build zig from source and I get the same output:

../zig/build-master/stage3/bin/zig version
0.14.0-dev.839+a931bfada

../zig/build-master/stage3/bin/zig build preprocess

roc run examples/roc/main.roc
🔨 Rebuilding platform...
Segmentation fault at address 0x7748756ce098
/home/ossi/src/zig/build-master/stage3/lib/zig/compiler_rt/memcpy.zig:14:9: 0x5d23a1a51f48 in memcpy (compiler_rt)
    if (len != 0) {
        ^
Unwind error at address `:0x5d23a1a51f48` (error.InvalidCFA), trace may be incomplete

Oskar Hahn (Aug 04 2024 at 07:39):

I think I found a solution.

When I use zig 0.11.0 and set dynhost.disable_stack_probing = true; (dynhost is the compiling step), it works.

They removed this option somewhere between 0.11.0 and 0.13.0. I have to check if there is an alternative.

Oskar Hahn (Aug 04 2024 at 07:55):

Ok. Found it. They changed the option in this commit. The new way to disable stack probing is with dynhost.root_module.stack_check = false;

Luke Boswell (Aug 04 2024 at 09:47):

This fixed a number of failing tests on the llvm upgrade branch. :smiley:

Oskar Hahn (Aug 04 2024 at 09:47):

Happy to help :heart_kiss:

Luke Boswell (Aug 04 2024 at 09:58):

Also gave me a good idea for another potential issue I'm looking into

Last updated: Jul 05 2025 at 12:14 UTC