ping?
On Tue, 6 Feb 2024 at 10:26, Christophe Lyon <christophe.l...@linaro.org> wrote:
>
> ping?
>
> On Thu, 25 Jan 2024 at 16:54, Christophe Lyon
> <christophe.l...@linaro.org> wrote:
> >
> > On Wed, 24 Jan 2024 at 12:02, Jonathan Wakely <jwak...@redhat.com> wrote:
> > >
> > > On Wed, 24 Jan 2024 at 10:48, Christophe Lyon wrote:
> > > >
> > > > GDB emits end of lines as \r\n, we currently match the reverse \n\r,
> > >
> > > We currently match [\n\r]+ which should match any of \n, \r, \n\r or \r\n
> > >
> >
> > Hmm, right, sorry I had this patch in my tree for quite some time, but
> > wrote the description just now, so I read a bit too quickly.
> >
> > >
> > > > possibly leading to mismatches under racy conditions.
> > >
> > > What do we incorrectly match? Is the problem that a \r\n sequence
> > > might be incompletely printed, due to buffering, and so the regex only
> > > sees (and matches) the \r which then leaves an unwanted \n in the
> > > stream, which then interferes with the next match? I don't understand
> > > why that problem wouldn't just result in a failed match with your new
> > > regex though.
> > >
> > Exactly: READ1 forces read() to return 1 byte at a time, so we leave
> > an unwanted \r in front of a string that should otherwise match the
> > "got" case.
> >
> > >
> > > >
> > > > I noticed this while running the GCC testsuite using the equivalent of
> > > > GDB's READ1 feature [1] which helps detecting bufferization issues.
> > > >
> > > > Adjusting the first regexp to match the right order implied fixing the
> > > > second one, to skip the empty lines.
> > >
> > > At the very least, this part of the description is misleading. The
> > > existing regex matches "the right order" already. The change is to
> > > match *exactly* \r\n instead of any mix of CR and LF characters.
> > > That's not about matching "the right order", it's being more precise
> > > in what we match.
> > >
> > > But I'm still confused about what the failure scenario is and how the
> > > change fixes it.
> > >
> >
> > I followed what the GDB testsuite does (it matches \r\n at the end of
> > many regexps), but in fact it seems it's not needed:
> > it works if I update the "got" regexp like this (ie. accept any number
> > of leading \r or \n):
> > - -re {^(type|\$([0-9]+)) = ([^\n\r]*)[\n\r]+} {
> > + -re {^[\n\r]*(type|\$([0-9]+)) = ([^\n\r]*)[\n\r]+} {
> > and leave the "skipping" regexp as it is currently.
> >
> > Is the new attached version OK?
> >
> > Thanks,
> >
> > Christophe
> >
> > > >
> > > > Tested on aarch64-linux-gnu.
> > > >
> > > > [1]
> > > > https//github.com/bminor/binutils-gdb/blob/master/gdb/testsuite/README#L269
> > > >
> > > > 2024-01-24 Christophe Lyon <christophe.l...@linaro.org>
> > > >
> > > > libstdc++-v3/
> > > > * testsuite/lib/gdb-test.exp (gdb-test): Fix regexps.
> > > > ---
> > > > libstdc++-v3/testsuite/lib/gdb-test.exp | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/libstdc++-v3/testsuite/lib/gdb-test.exp
> > > > b/libstdc++-v3/testsuite/lib/gdb-test.exp
> > > > index 31206f2fc32..0de8d9ee153 100644
> > > > --- a/libstdc++-v3/testsuite/lib/gdb-test.exp
> > > > +++ b/libstdc++-v3/testsuite/lib/gdb-test.exp
> > > > @@ -194,7 +194,7 @@ proc gdb-test { marker {selector {}} {load_xmethods
> > > > 0} } {
> > > >
> > > > set test_counter 0
> > > > remote_expect target [timeout_value] {
> > > > - -re {^(type|\$([0-9]+)) = ([^\n\r]*)[\n\r]+} {
> > > > + -re {^(type|\$([0-9]+)) = ([^\n\r]*)\r\n} {
> > > > send_log "got: $expect_out(buffer)"
> > > >
> > > > incr test_counter
> > > > @@ -250,7 +250,7 @@ proc gdb-test { marker {selector {}} {load_xmethods
> > > > 0} } {
> > > > return
> > > > }
> > > >
> > > > - -re {^[^$][^\n\r]*[\n\r]+} {
> > > > + -re {^[\r\n]*[^$][^\n\r]*\r\n} {
> > > > send_log "skipping: $expect_out(buffer)"
> > > > exp_continue
> > > > }
> > > > --
> > > > 2.34.1
> > > >
> > >
