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perl5db.pl: b subname and c subname break on first executable line
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This currently doesn't try to handle "b postpone subname" since that
internally has an offset function that doesn't really work
with this implementation.

This is a partial fix for Perl#799
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@tonycoz
tonycoz committed Jul 4, 2024
1 parent 07523af commit 8c516c3
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Showing 2 changed files with 125 additions and 20 deletions.
86 changes: 66 additions & 20 deletions lib/perl5db.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -2033,19 +2033,12 @@ sub _DB__handle_c_command {
# Qualify it to the current package unless it's
# already qualified.
$subname = $package . "::" . $subname
unless $subname =~ /::/;
unless $subname =~ /::/;

# find_sub will return "file:line_number" corresponding
# to where the subroutine is defined; we call find_sub,
# break up the return value, and assign it in one
# operation.
( $file, $i ) = ( find_sub($subname) =~ /^(.*):(.*)$/ );

# Force the line number to be numeric.
$i = $i + 0;
my ($file, $s, $e) = do { subroutine_first_breakable_line($subname) };

# If we got a line number, we found the sub.
if ($i) {
if ($s) {

# Switch all the debugger's internals around so
# we're actually working with that file.
Expand All @@ -2058,19 +2051,18 @@ sub _DB__handle_c_command {
# Scan forward to the first executable line
# after the 'sub whatever' line.
$max = $#dbline;
my $_line_num = $i;
while ($dbline[$_line_num] == 0 && $_line_num< $max)
my $_line_num = $s;
while ($dbline[$_line_num] == 0 && $_line_num <= $e)
{
$_line_num++;
}
$i = $_line_num;
} ## end if ($i)

# We didn't find a sub by that name.
else {
print $OUT "Subroutine $subname not found.\n";
next CMD;
print $OUT $@;
next CMD;
}

} ## end if ($subname =~ /\D/)

# At this point, either the subname was all digits (an
Expand Down Expand Up @@ -5389,6 +5381,61 @@ sub subroutine_filename_lines {
return (find_sub($subname) =~ /^(.*):(\d+)-(\d+)$/);
} ## end sub subroutine_filename_lines

=head2 subroutine_first_breakable(subname)
Return the file and line number of the first breakable line in
subname.
Throws an error message if subname is not breakable, or cannot be
found.
=cut

sub _first_breakable_via_B {
my ( $subname ) = @_;

my $cv = do {
no strict "refs";
*$subname{CODE};
};
ref $cv eq "CODE"
or return;

eval { require B; 1 }
or return;

my $bcv = B::svref_2object($cv);

# can't break on an XSUB
$bcv->XSUB
and die "Cannot break on XSUB $subname\n";

my $op = $bcv->START;
unless ($op->isa("B::NULL")) {
while (!$op->isa("B::NULL") && $op->name ne "dbstate") {
$op = $op->next;
}

unless ($op->isa("B::NULL")) {
return ( $op->file, $op->line, $op->line );
}
}
return;
}

sub subroutine_first_breakable_line {
my ( $subname ) = @_;

my ($file, $s, $e) = _first_breakable_via_B($subname);
unless ($file) {
# at the very least this allows miniperl to debug
( $file, $s, $e ) = subroutine_filename_lines($subname)
or die "Subroutine $subname not found.\n";
}

return ($file, $s, $e );
}

=head3 break_subroutine(subname) (API)
Places a break on the first line possible in the specified subroutine. Uses
Expand All @@ -5401,9 +5448,8 @@ sub break_subroutine {
my $subname = shift;

# Get filename, start, and end.
my ( $file, $s, $e ) = subroutine_filename_lines($subname)
or die "Subroutine $subname not found.\n";

my ( $file, $s, $e ) = eval { subroutine_first_breakable_line($subname) }
or die $@;

# Null condition changes to '1' (always true).
my $cond = @_ ? shift(@_) : 1;
Expand Down Expand Up @@ -8849,7 +8895,7 @@ =head2 C<find_sub>
Tries to use C<%sub> first; if it can't find it there, it tries building a
reference to the subroutine and uses C<CvGV_name_or_bust> to locate it,
loading it into C<@sub> as a side effect (XXX I think). If it can't find it
loading it into C<%sub> as a side effect (XXX I think). If it can't find it
this way, it brute-force searches C<%sub>, checking for identical references.
=cut
Expand Down
59 changes: 59 additions & 0 deletions lib/perl5db.t
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Original file line number Diff line number Diff line change
Expand Up @@ -3491,6 +3491,65 @@ EOS
$wrapper->output_like(qr/\bOK\b/, "check the line is IOK");
}

{
# https://github.com/Perl/perl5/issues/799
my $prog = <<'EOS';
sub problem {
$SIG{__DIE__} = sub {
die "<b problem> will set a break point here.\n";
}; # The break point _should_ be set here.
warn "This line will run even if you enter <c problem>.\n";
}
&problem;
EOS

my $wrapper = DebugWrap->new(
{
cmds =>
[
"b problem",
"c",
"q"
],
prog => \$prog
}
);
$wrapper->contents_like(qr/The break point _should_/, "break at right place (b)");
$wrapper->output_unlike(qr/This line will run even if you enter <c problem>\./,
"didn't run the wrong code (b)");

$wrapper = DebugWrap->new(
{
cmds =>
[
"c problem",
"q"
],
prog => \$prog
}
);
$wrapper->contents_like(qr/The break point _should_/, "break at right place (c)");
$wrapper->output_unlike(qr/This line will run even if you enter <c problem>\./,
"didn't run the wrong code (c)");
}

{
my $wrapper = DebugWrap->new(
{
cmds =>
[
"b B::svref_2object",
"q"
],
prog => \<<'EOS'
use B;
print "Hello\n";
EOS
}
);
$wrapper->contents_like(qr/Cannot break on XSUB B::svref_2object/, "can't break on XSUB");
}

done_testing();

END {
Expand Down

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