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Postings from October 2014
# New Ticket Created by l.mai@web.de
# Please include the string: [perl #122966]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=122966 >
The Problem
-----------
Consider this code:
#!perl
use strict;
use warnings;
if (1 {
my $wtf = 42;
print "$wtf\n";
}
__END__
If you run that, you get:
"my" variable $wtf masks earlier declaration in same statement at foo.pl line 7.
syntax error at foo.pl line 5, near "1 {"
syntax error at foo.pl line 8, near "}"
Execution of foo.pl aborted due to compilation errors.
I.e. there's a bogus warning on line 7, then the actual error on line 5.
Now the same code with fatal warnings:
#!perl
use strict;
use warnings FATAL => 'all';
if (1 {
my $wtf = 42;
print "$wtf\n";
}
__END__
This time the output is just:
"my" variable $wtf masks earlier declaration in same statement at bar.pl line 7.
The actual error is completely hidden because the bogus warning throws an exception and aborts everything.
My Solution
-----------
I've attached a patch that solves this problem by simply defatalizing warnings if we're currently parsing and there are pending parse errors. I think this is a good way to handle this situation because we don't know whether the warning we're about to emit is useful or caused by misinterpretation of the code after a syntax error. So we warn non-fatally because the pending parse errors will throw an exception later on anyway.
Thoughts?
(Patch copied inline here because I don't know whether attaching or inline code is the preferred method.)
>From f3aa466b4080470e3a14071cb476674e9bfdf796 Mon Sep 17 00:00:00 2001
From: Lukas Mai <l.mai@web.de>
Date: Sun, 12 Oct 2014 19:01:09 +0200
Subject: [PATCH] don't fatalize warnings after syntax errors
---
util.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/util.c b/util.c
index ae3b833..0689d7c 100644
--- a/util.c
+++ b/util.c
@@ -1911,7 +1911,8 @@ Perl_vwarner(pTHX_ U32 err, const char* pat, va_list* args)
{
dVAR;
PERL_ARGS_ASSERT_VWARNER;
- if (PL_warnhook == PERL_WARNHOOK_FATAL || ckDEAD(err)) {
+ if ((PL_warnhook == PERL_WARNHOOK_FATAL || ckDEAD(err))
+ && !(PL_parser && PL_parser->error_count)) {
SV * const msv = vmess(pat, args);
invoke_exception_hook(msv, FALSE);
--
2.1.2
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