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authorChris Down <chris@chrisdown.name>2023-01-28 12:53:48 +0100
committerHiltjo Posthuma <hiltjo@codemadness.org>2023-01-28 13:34:43 +0100
commit712d6639ff8e863560328131bbb92b248dc9cde7 (patch)
treec563872871c1e3e947d40caae45614498140e8dd /%3fid%3d712d6639ff8e863560328131bbb92b248dc9cde7?id=712d6639ff8e863560328131bbb92b248dc9cde7
parent89f9905714c1c1b2e8b09986dfbeca15b68d8af8 (diff)
Use sigaction(SA_NOCLDWAIT) for SIGCHLD handling
signal() semantics are pretty unclearly specified. For example, depending on OS kernel and libc, the handler may be returned to SIG_DFL (hence the inner call to read the signal handler). Moving to sigaction() means the behaviour is consistently defined. Using SA_NOCLDWAIT also allows us to avoid calling the non-reentrant function die() in the handler. Some addditional notes for archival purposes: * NRK pointed out errno of waitpid could also theoretically get clobbered. * The original patch was iterated on and modified by NRK and Hiltjo: * SIG_DFL was changed to SIG_IGN, this is required, atleast on older systems such as tested on Slackware 11. * signals are not blocked using sigprocmask, because in theory it would briefly for example also ignore a SIGTERM signal. It is OK if waitpid() is (in theory interrupted). POSIX reference: "Consequences of Process Termination": https://pubs.opengroup.org/onlinepubs/9699919799/functions/_Exit.html#tag_16_01_03_01
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