[ruby-core:112171] [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).


```
I am using Centos 7.8 and further investigations shows that the problem occurs when
soft and hard limits are equal. In our case 157286400.
Lowering the softlimit will make ruby run without error.
I have made similar tes on Ffedora 36 and here the code runs without problems.

Se the following from Centos

cat /proc/self/limits 

Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            157286400            157286400            bytes     
Max core file size        unlimited            unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             688754               688754               processes 
Max open files            32768                32768                files     
Max locked memory         unlimited            unlimited            bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       688754               688754               signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us   
     
./ruby -h
Segmentation fault (core dumped)

ulimit -S -s 1572    

./ruby -h

Usage: /home/projects/sysadmin/people/johnd/ruby/ruby [switches] [--] [programfile] [arguments]
  -0[octal]       specify record separator (\0, if no argument)
  -a              autosplit mode with -n or -p (splits $_ into $F)
  -c              check syntax only
  -Cdirectory     cd to directory before executing your script
  -d              set debugging flags (set $DEBUG to true)
  -e 'command'    one line of script. Several -e's allowed. Omit [programfile]
  -Eex[:in]       specify the default external and internal character encodings
  -Fpattern       split() pattern for autosplit (-a)
  -i[extension]   edit ARGV files in place (make backup if extension supplied)
  -Idirectory     specify $LOAD_PATH directory (may be used more than once)
  -l              enable line ending processing
  -n              assume 'while gets(); ... end' loop around your script
  -p              assume loop like -n but print line also like sed
  -rlibrary       require the library before executing your script
  -s              enable some switch parsing for switches after script name
  -S              look for the script using PATH environment variable
  -v              print the version number, then turn on verbose mode
  -w              turn warnings on for your script
  -W[level=2|:category]     set warning level; 0=silence, 1=medium, 2=verbose
  -x[directory]   strip off text before #!ruby line and perhaps cd to directory
  --jit           enable JIT for the platform, same as --mjit (experimental)
  --mjit          enable C compiler-based JIT compiler (experimental)
  -h              show this message, --help for more info


 cat /proc/self/limits 
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            1609728              157286400            bytes     
Max core file size        unlimited            unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             688754               688754               processes 
Max open files            32768                32768                files     
Max locked memory         unlimited            unlimited            bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       688754               688754               signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us   
``` 

----------------------------------------
Bug #19397: ruby -h fails with SIGSGV if ulimit -s is any else than unlimited
https://bugs.ruby-lang.org/issues/19397#change-101607

* 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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