RFR: 8338883: Show warning when CreateCoredumpOnCrash set, but core dump will not happen [v14]

[Gerard Ziemski]

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> We add a small feature, which prints a warning if user explicitly requests `CreateCoredumpOnCrash`, but it's disabled on the os level.
> 
> This behavior is the same as other VM features that can be turned on by runtime flags, but are unavailable. For example we show `"UseCRC32 specified, but not supported on this CPU"` if `UseCRC32` is set, but unavailable.
> 
> Example of output:
> 
> 
> # ulimit -c 0                                                         
> # ./build/xcode/build/jdk/bin/java -XX:+CreateCoredumpOnCrash -version
> OpenJDK 64-Bit Server VM warning: CreateCoredumpOnCrash specified, but Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
> openjdk version "24-internal" 2025-03-18
> OpenJDK Runtime Environment (build 24-internal-adhoc.gerard.jdk)
> OpenJDK 64-Bit Server VM (build 24-internal-adhoc.gerard.jdk, mixed mode, sharing)
> 
> # ulimit -c 1024                                                      
> # ./build/xcode/build/jdk/bin/java -XX:+CreateCoredumpOnCrash -version
> OpenJDK 64-Bit Server VM warning: CreateCoredumpOnCrash specified, but /cores/core.66547 (max size 512 k). To ensure a full core dump, try "ulimit -c unlimited" before starting Java again
> openjdk version "24-internal" 2025-03-18
> OpenJDK Runtime Environment (build 24-internal-adhoc.gerard.jdk)
> OpenJDK 64-Bit Server VM (build 24-internal-adhoc.gerard.jdk, mixed mode, sharing)
> 
> # ulimit -c unlimited
> # ./build/xcode/build/jdk/bin/java -XX:+CreateCoredumpOnCrash -version
> openjdk version "24-internal" 2025-03-18
> OpenJDK Runtime Environment (build 24-internal-adhoc.gerard.jdk)
> OpenJDK 64-Bit Server VM (build 24-internal-adhoc.gerard.jdk, mixed mode, sharing)
> 
> 
> 
> 
> 
> Testing:
> - passes `"MACH5 runtime/ErrorHandling/CreateCoredumpOnCrash.java"`
> - full MACH5 test in progress...

Gerard Ziemski has updated the pull request incrementally with one additional commit since the last revision:

  change how we call ulimit, relax the checks to accommodate get_core_path() code paths

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20734/files
  - new: https://git.openjdk.org/jdk/pull/20734/files/6140c609..8534c143

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20734&range=13
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20734&range=12-13

  Stats: 4 lines in 1 file changed: 1 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20734.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20734/head:pull/20734

PR: https://git.openjdk.org/jdk/pull/20734