RFR: 8364611: (process) Child process SIGPIPE signal disposition should be default

[Roger Riggs]

On Mon, 4 Aug 2025 08:40:13 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> A customer reported an error where a well-known system library, upon loading into the JVM process (via a longish indirect dependency chain), changed the signal disposition of the process for SIGPIPE to SIG_IGN. This gets inherited down to child processes, where it caused child processes to not react to SIGPIPE.
> 
> The system library is clearly at fault here, but the current workaround we recommend (pre-loading libjsig to interpose incorrect signal handling requests) is impractical for many customers. It is an okay solution when customers themselves have uncommon signal handling requirements; but for cases like these, where some version of system library does that, we should have a more pragmatic solution.
> 
> See further details and arguments for the fix in this mail thread: https://mail.openjdk.org/pipermail/core-libs-dev/2025-April/144077.html .
> 
> The behavior is changed changed such that we set SIGPIPE to SIG_DFL in the child processes, and a regression test is added. Note: Regression test deliberately prints outs details for other POSIX signals too; this can be both a good ad-hoc analysis tool as well as a point where we add more tests for other signals, should we ever need to. This patch, however, is deliberately restricted to just fixing SIGPIPE.

src/java.base/unix/native/libjava/childproc.c line 429:

> 427:     }
> 428: 
> 429:     // Childs should be started with default signal disposition for SIGPIPE

Editorial: "Childs" -> Children for plural, "Child" for singular.  Here and in tests.

test/jdk/java/lang/ProcessBuilder/childSignalDisposition/exePrintSignalDisposition.c line 60:

> 58:         struct sigaction act;
> 59:         if (sigaction(signals[n].sig, NULL, &act) != 0) {
> 60:             perror("sigaction");

The sigaction error message goes to stderr, so it is does not appear in line with the signal name.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26615#discussion_r2257297399
PR Review Comment: https://git.openjdk.org/jdk/pull/26615#discussion_r2257335209