diff options
author | Ian Jackson <ijackson@chiark.greenend.org.uk> | 2016-07-16 23:10:27 +0100 |
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committer | Ian Jackson <ijackson@chiark.greenend.org.uk> | 2016-07-17 13:46:14 +0100 |
commit | 0658281163715a24c940509ebb8b0a7493e33787 (patch) | |
tree | 083e71018282942a6968dfab55af98e96467449f /Debian/Dgit.pm | |
parent | 6bce7517ee43b52e0a23c74dec8f5d0bcb7d0668 (diff) |
Subprocess error handling: Initialise $? to -1
When system(3perl) fails due to syscall error, it sets only $!. When
it succeeds it sets only $? and sometimes trashes $!. Conversely,
close of a popened filehandle always sets both in all cases.
Document this in a comment.
So when using system and relying on $?/$! (rather than looking at
system's return value), such as when about to use failedcmd, it's
necessary to initialise $? to -1.
Fix the three call sites where system might be followed by failedcmd
but this wasn't done.
Diffstat (limited to 'Debian/Dgit.pm')
-rw-r--r-- | Debian/Dgit.pm | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/Debian/Dgit.pm b/Debian/Dgit.pm index 2555812..aa0c5a3 100644 --- a/Debian/Dgit.pm +++ b/Debian/Dgit.pm @@ -186,8 +186,19 @@ sub waitstatusmsg () { } sub failedcmd { + # Expects $!,$? as set by close - see below. + # To use with system(), set $?=-1 first. + # + # Actual behaviour of perl operations: + # success $!==0 $?==0 close of piped open + # program failed $!==0 $? >0 close of piped open + # syscall failure $! >0 $?=-1 close of piped open + # failure $! >0 unchanged close of something else + # success trashed $?==0 system + # program failed trashed $? >0 system + # syscall failure $! >0 unchanged system { local ($!); printcmd \*STDERR, _us().": failed command:", @_ or die $!; }; - if ($!) { + if ($? < 0) { fail "failed to fork/exec: $!"; } elsif ($?) { fail "subprocess ".waitstatusmsg(); |