Thanks for the patch. Comments below.
On Sun, 4 Sept 2022 at 19:48, Philipp Fent via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> Signed-off-by: Philipp Fent <f...@in.tum.de>
> ---
> libstdc++-v3/python/libstdcxx/v6/printers.py | 37 +++++++++++++++++++
> .../libstdc++-prettyprinters/debug.cc | 5 +++
> .../libstdc++-prettyprinters/simple.cc | 5 +++
> .../libstdc++-prettyprinters/simple11.cc | 5 +++
> 4 files changed, 52 insertions(+)
>
> diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py
> b/libstdc++-v3/python/libstdcxx/v6/printers.py
> index d70c8d5d616..5083f693387 100644
> --- a/libstdc++-v3/python/libstdcxx/v6/printers.py
> +++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
> @@ -969,6 +969,39 @@ class StdStringPrinter:
> def display_hint (self):
> return 'string'
>
> +class StdStringBufPrinter:
> + "Print a std::basic_stringbuf"
> +
> + def __init__(self, _, val):
> + self.val = val
> +
> + def to_string(self):
> + pbase = self.val['_M_out_beg']
> + pptr = self.val['_M_out_cur']
> + egptr = self.val['_M_in_end']
It would be nice to encapsulate this into a generic helper for all
streambufs, as this part isn't specific to basic_stringbuf. We could
then reuse it for printing spanbufs and other types in future. It
could be a function that takes a streambuf and returns a tuple of
(pbase, pptr, egptr).
> + # Logic from basic_stringbuf::_M_high_mark()
> + if pptr:
> + if not egptr or pptr > egptr:
> + return pbase.string(length = pptr - pbase)
> + else:
> + return pbase.string(length = pptr - egptr)
Shouldn't this be egptr - pbase?
This suggests the tests are inadequate. I think this bug would have
been found by a test something like:
std::stringstream ssin("input", std::ios::in);
// { dg-final { note-test ssin "\"input\"" } }
The (egptr - pbase) case is also needed for printing an istringstream.
> + return self.val['_M_string']
> +
> + def display_hint(self):
> + return 'string'
> +
> +class StdStringStreamPrinter:
> + "Print a std::basic_stringstream"
> +
> + def __init__(self, _, val):
> + self.val = val
> +
> + def to_string(self):
> + return self.val['_M_stringbuf']
This assumes that the stream is still using its stringbuf, which is
probably true 99% of the time, but isn't guaranteed. In the following
situation, the printer would give potentially misleading output:
std::stringstream ss("xxx");
ss.rdbuf(std::cin.rdbuf());
I wonder if we want to have a check that self.val['_M_streambuf'] ==
self.val['_M_stringbuf'].address
Alternatively, don't provide a printer for the stringstream at all,
just for the stringbuf, and then when GDB uses its default display for
the stringstream it will show that member.
> +
> + def display_hint(self):
> + return 'string'
> +
> class Tr1HashtableIterator(Iterator):
> def __init__ (self, hashtable):
> self.buckets = hashtable['_M_buckets']
> @@ -2232,6 +2265,10 @@ def build_libstdcxx_dictionary ():
> libstdcxx_printer.add_version('std::', 'initializer_list',
> StdInitializerListPrinter)
> libstdcxx_printer.add_version('std::', 'atomic', StdAtomicPrinter)
> + libstdcxx_printer.add_version('std::', 'basic_stringbuf',
> StdStringBufPrinter)
> + libstdcxx_printer.add_version('std::__cxx11::', 'basic_stringbuf',
> StdStringBufPrinter)
> + libstdcxx_printer.add_version('std::', 'basic_stringstream',
> StdStringStreamPrinter)
> + libstdcxx_printer.add_version('std::__cxx11::', 'basic_stringstream',
> StdStringStreamPrinter)
Wouldn't we want it for ostringstream and istringstream too?
