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* fix return value of system on failure to spawn child processRich Felker2018-08-281-1/+1
| | | | | | | | | | | | | the value 0x7f00 (as if by _exit(127)) is specified only for the case where the child is created but then fails to exec the shell, since traditional fork+exec implementations do not admit reporting an error via errno in this case without additional machinery. it's unclear whether an implementation not subject to this failure mode needs to emulate it; one could read the standard as requiring that. if so, additional code will need to be added to map posix_spawn errors into the form system is expected to return. but for now, returning -1 to indicate an error is significantly better behavior than always reporting failures as if the shell failed to exec after fork.
* include cleanups: remove unused headers and add feature test macrosSzabolcs Nagy2013-12-121-1/+1
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* remove cruft from pre-posix_spawn version of the system functionRich Felker2013-03-241-6/+0
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* consistently use the internal name __environ for environRich Felker2013-02-171-2/+2
| | | | | | | | | | | patch by Jens Gustedt. previously, the intended policy was to use __environ in code that must conform to the ISO C namespace requirements, and environ elsewhere. this policy was not followed in practice anyway, making things confusing. on top of that, Jens reported that certain combinations of link-time optimization options were breaking with the inconsistent references; this seems to be a compiler or linker bug, but having it go away is a nice side effect of the changes made here.
* base system() on posix_spawnRich Felker2013-02-031-41/+26
| | | | | this avoids duplicating the fragile logic for executing an external program without fork.
* system is a cancellation pointRich Felker2012-10-281-0/+3
| | | | | | | | | | ideally, system would also be cancellable while running the external command, but I cannot find any way to make that work without either leaking zombie processes or introducing behavior that is far outside what the standard specifies. glibc handles cancellation by killing the child process with SIGKILL, but this could be unsafe in that it could leave the data being manipulated by the command in an inconsistent state.
* fix usage of locks with vforkRich Felker2012-10-191-1/+2
| | | | | | __release_ptc() is only valid in the parent; if it's performed in the child, the lock will be unlocked early then double-unlocked later, corrupting the lock state.
* overhaul system() and popen() to use vfork; fix various related bugsRich Felker2012-10-181-23/+42
| | | | | | | | | | | | | | | | since we target systems without overcommit, special care should be taken that system() and popen(), like posix_spawn(), do not fail in processes whose commit charges are too high to allow ordinary forking. this in turn requires special precautions to ensure that the parent process's signal handlers do not end up running in the shared-memory child, where they could corrupt the state of the parent process. popen has also been updated to use pipe2, so it does not have a fd-leak race in multi-threaded programs. since pipe2 is missing on older kernels, (non-atomic) emulation has been added. some silly bugs in the old code should be gone too.
* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-121-0/+45