| Message ID | 20240124104750.1024129-1-christophe.lyon@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [testsuite] Fix pretty printers regexps for GDB output | expand |
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 > 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. > > 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. > > Tested on aarch64-linux-gnu. > > [1] https//github.com/bminor/binutils-gdb/blob/master/gdb/testsuite/README#L269 > > 2024-01-24 Christophe Lyon <christophe.lyon@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 >
On Wed, 24 Jan 2024 at 12:02, Jonathan Wakely <jwakely@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.lyon@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 > > >
ping? On Thu, 25 Jan 2024 at 16:54, Christophe Lyon <christophe.lyon@linaro.org> wrote: > > On Wed, 24 Jan 2024 at 12:02, Jonathan Wakely <jwakely@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.lyon@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 > > > > >
ping? On Tue, 6 Feb 2024 at 10:26, Christophe Lyon <christophe.lyon@linaro.org> wrote: > > ping? > > On Thu, 25 Jan 2024 at 16:54, Christophe Lyon > <christophe.lyon@linaro.org> wrote: > > > > On Wed, 24 Jan 2024 at 12:02, Jonathan Wakely <jwakely@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.lyon@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 > > > > > > >
On Thu, 25 Jan 2024 at 15:54, Christophe Lyon <christophe.lyon@linaro.org> wrote: > > On Wed, 24 Jan 2024 at 12:02, Jonathan Wakely <jwakely@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? Yeah this makes more sense to me now, thanks. OK for trunk. > > 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.lyon@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 > > > > >
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 }