[release/0.25] fix: reset inherited signal dispositions for forked processes on macOS - #245
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David Negstad (danegsta) merged 2 commits intoAug 20, 2026
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On macOS, processes started by 'dcp fork-process' inherited the Go runtime's signal handler flags (SA_SIGINFO|SA_ONSTACK|SA_RESTART). Other language runtimes do not expect to start with those flags set, and NativeAOT .NET binaries crash with SIGSEGV the first time they take a GC suspension via SIGUSR1. Clearing the dispositions in 'fork-process' before starting the child does not help, because the Go runtime restores its own dispositions in the forked child before it reaches execve. The reset has to happen in the process that calls exec, so 'fork-process' now routes the child through a hidden 'fork-process-exec' command that clears the dispositions and then execs the requested program. Since execve keeps the process ID, the reported PID, session, standard streams, and exit code all stay the same. The reset is a no-op on other platforms, where children are started directly as before. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: fcd61592-fa3e-49ab-8efc-d21136bb147d
Routing the child through the exec shim made every start look successful, because the process being started became dcp itself, which always exists and is executable. A program that could not be run was reported as started and its PID was written to stdout, even though the process exited immediately. Commands are given absolute paths, which skip the PATH lookup that used to catch this before the child was started. The shim now reports the outcome of the exec on an inherited descriptor: a successful execve closes it, and a failure sends the errno first. 'fork-process' waits for that before reporting the PID, so a program that cannot be executed is once again a start failure carrying the original reason. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: fcd61592-fa3e-49ab-8efc-d21136bb147d
David Negstad (danegsta)
requested a review
from Karol Zadora-Przylecki (karolz-ms)
August 19, 2026 23:34
Karol Zadora-Przylecki (karolz-ms)
approved these changes
Aug 19, 2026
David Negstad (danegsta)
enabled auto-merge (squash)
August 20, 2026 00:25
David Negstad (danegsta)
merged commit Aug 20, 2026
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release/0.25
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Backport of #244 to release/0.25
/cc David Negstad (@danegsta)
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