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Re: [PATCH 3/4] start_command: detect execvp failures early

From
Junio C Hamano <gitster@pobox.com>
Date
Jan 14, 2010, 22:40 UTC
Message-ID
<7vska88g4k.fsf@alter.siamese.dyndns.org>
In-Reply-To
<201001142253.19595.j6t@kdbg.org>
Johannes Sixt <j6t@kdbg.org> writes:
Show 13 quoted lines
> On Donnerstag, 14. Januar 2010, Junio C Hamano wrote:
>> Johannes Sixt <j6t@kdbg.org> writes:
>> > Previously, failures during execvp could be detected only by
>> > finish_command. However, in some situations it is beneficial for the
>> > parent process to know earlier that the child process will not run.
>> >
>> > The idea to use a pipe to signal failures to the parent process and
>> > the test case were lifted from patches by Ilari Liusvaara.
>>
>> I wonder if we can do this without pipe, perhaps using "vfork, exec, then
>> update a variable"....
>
> Except that some systems implement vfork(2) in terms of fork(2), I heard.

As long as they implement it correctly, we don't care if it is implemented in terms of fork or knife or chopstick. The only thing we care about in this crazy-idea was the shared address space the child can write into until it exec or _exit while the parent is in a frozen state.

> Moreover, I think that we do way too many things before the exec; isn't that 
> dangerous?

Yeah, we do seem to do quite a lot more than I thought. Scratch that crazy idea, then.

Previous: Johannes SixtNext: Johannes Sixt
Message 9 of 11 in “Imporove remote helper exec failure reporting”
  1. 0/2 Imporove remote helper exec failure reportingIlari Liusvaara, Jan 9, 2010
  2. 1/2 Report exec errors from run-commandIlari Liusvaara, Jan 9, 2010
  3. 0/4 Detect exec errors in start_command earlyJohannes Sixt, Jan 10, 2010
  4. 1/4 start_command: report child process setup errors to the parent's stderrJohannes Sixt, Jan 10, 2010
  5. 2/4 run-command: move wait_or_whine earlierJohannes Sixt, Jan 10, 2010
  6. 3/4 start_command: detect execvp failures earlyJohannes Sixt, Jan 10, 2010
  7. Junio C HamanoJan 14, 2010
  8. Johannes SixtJan 14, 2010
  9. Junio C HamanoJan 14, 2010
  10. 4/4 Improve error message when a transport helper was not foundJohannes Sixt, Jan 10, 2010
  11. 2/2 Improve transport helper exec failure reportingIlari Liusvaara, Jan 9, 2010

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