diff options
| -rw-r--r-- | pod/perlvar.pod | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/pod/perlvar.pod b/pod/perlvar.pod index 5f48dad7c0..930b823857 100644 --- a/pod/perlvar.pod +++ b/pod/perlvar.pod @@ -607,7 +607,8 @@ The hash C<%SIG> contains signal handlers for signals. For example: Using a value of C<'IGNORE'> usually has the effect of ignoring the signal, except for the C<CHLD> signal. See L<perlipc> for more about -this special case. +this special case. Using an empty string or C<undef> as the value has +the same effect as C<'DEFAULT'>. Here are some other examples: @@ -622,6 +623,11 @@ Here are some other examples: Be sure not to use a bareword as the name of a signal handler, lest you inadvertently call it. +Using a string that doesn't correspond to any existing function or a +glob that doesn't contain a code slot is equivalent to C<'IGNORE'>, +but a warning is emitted when the handler is being called (the warning +is not emitted for the internal hooks described below). + If your system has the C<sigaction()> function then signal handlers are installed using it. This means you get reliable signal handling. @@ -640,8 +646,9 @@ errors, like this: local $SIG{__WARN__} = sub { die $_[0] }; eval $proggie; -As the C<'IGNORE'> hook is not supported by C<__WARN__>, you can -disable warnings using the empty subroutine: +As the C<'IGNORE'> hook is not supported by C<__WARN__>, its effect is +the same as using C<'DEFAULT'>. You can disable warnings using the +empty subroutine: local $SIG{__WARN__} = sub {}; @@ -661,6 +668,9 @@ at a distance like rewriting a pending exception in C<$@>. Plans to rectify this have been scrapped, as users found that rewriting a pending exception is actually a useful feature, and not a bug. +The C<$SIG{__DIE__}> doesn't support C<'IGNORE'>, it has the same +effect as C<'DEFAULT'>. + C<__DIE__>/C<__WARN__> handlers are very special in one respect: they may be called to report (probable) errors found by the parser. In such a case the parser may be in inconsistent state, so any attempt to |