[ruby-core:112181] [Ruby master Bug#19397] ruby -h fails with SIGSGV if ulimit -s is any else than unlimited

Issue #19397 has been updated by john_d_s (John Damm Soerensen).


We see it on all of our systems.
But it gets stranger as it turns out to only happen in an interactive shell and not when executed in a shell script.
Furthermore it seems to only happen with certain combinations of soft and hard limits, though I have figured out which, but 8192/8192 also works on our systems.

For reference the build was done as per instruction in the ./doc/contributing/building_ruby.md 

I have looked at the offending code in thread_pthread.c and it is using alloca() which use according to the manual is highly discouraged.
Since the code is only invoked in cases where the stack limit is not unlimited/infinity it seems not to be needed. Therefor I suggest that to consider removing the code.

Anyway we have a workaround and you can close the case.


----------------------------------------
Bug #19397: ruby -h fails with SIGSGV if ulimit -s is any else than unlimited
https://bugs.ruby-lang.org/issues/19397#change-101618

* Author: john_d_s (John Damm Soerensen)
* Status: Feedback
* Priority: Normal
* ruby -v: ruby 3.3.0dev (2023-01-30T23:43:40Z master 7439ccf0ed) [x86_64-linux]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
This applies to all versions of ruby.
I have tried these  2.6.3  2.6.6  2.7.2  3.0.0  3.2.0

To reproduce simply set `ulimit -s` to anything other than unlimited.

Then run `ruby -h` (or any other invocation of ruby) and ruby will generate a SIGSEGV and core dump.

The stack trace from gdb shows that ruby has failed in reserve_stack line 1022 (for the latest from github)
gdb ruby core.11885 

```
Core was generated by `./ruby -h'.
Program terminated with signal 11, Segmentation fault.
#0  reserve_stack (limit=0x7e9a5f4400e0 <Address 0x7e9a5f4400e0 out of bounds>, 
    limit@entry=0x7fffffffe000 "l=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.axv=38;5;13:*.anx=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.mid=38;5;45:*.midi=3"..., size=1535999991552, size@entry=1535999995904)
    at thread_pthread.c:1022
1022	            limit[0] = 0;
```



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