grep: -P: report input filename upon PCRE execution failure

Without this, it could be tedious to determine which input
file evokes a PCRE-execution-time failure.
* src/pcresearch.c (Pexecute): When failing, include the
error-provoking file name in the diagnostic.
* src/grep.c (input_filename): Make extern, since used above.
* src/search.h (input_filename): Declare.
* tests/filename-lineno.pl: Test for this.
($no_pcre): Factor out.
* NEWS (Bug fixes): Mention this.

1 files changed, 13 insertions, 2 deletions

diff --git a/tests/filename-lineno.pl b/tests/filename-lineno.pl
index d44dd7b7..42d1b046 100755
--- a/tests/filename-lineno.pl
+++ b/tests/filename-lineno.pl
@@ -37,6 +37,8 @@ $prog = $full_prog_name if $full_prog_name;
 # Transform each to this: "Unmatched [..."
 my $err_subst = {ERR_SUBST => 's/(: Unmatched \[).*/$1.../'};
 
+my $no_pcre = "$prog: Perl matching not supported in a --disable-perl-regexp build\n";
+
 my @Tests =
   (
    # Show that grep now includes filename:lineno in the diagnostic:
@@ -100,13 +102,22 @@ my @Tests =
    ['invalid-re-P-paren', '-P ")"', {EXIT=>2},
     {ERR => $ENV{PCRE_WORKS} == 1
        ? "$prog: unmatched parentheses\n"
-       : "$prog: Perl matching not supported in a --disable-perl-regexp build\n"
+       : $no_pcre
     },
    ],
    ['invalid-re-P-star-paren', '-P "a.*)"', {EXIT=>2},
     {ERR => $ENV{PCRE_WORKS} == 1
        ? "$prog: unmatched parentheses\n"
-       : "$prog: Perl matching not supported in a --disable-perl-regexp build\n"
+       : $no_pcre
+    },
+   ],
+
+   # Prior to grep-3.6, the name of the offending file was not printed.
+   ['backtracking-with-file', '-P "((a+)*)+$"', {EXIT=>2},
+    {IN=>{f=>"a"x20 ."b"}},
+    {ERR => $ENV{PCRE_WORKS} == 1
+       ? "$prog: f: exceeded PCRE's backtracking limit\n"
+       : $no_pcre
     },
    ],