Re: gdb builder status (Was: Adding binutils to the GNU Toolchain buildbot on sourceware)

Hi,

On Fri, Apr 29, 2022 at 10:04:22PM +0200, Mark Wielaard via Overseers wrote:
> The fedora-s390x failure looks as follows:
> https://builder.sourceware.org/buildbot/#/builders/gdb-fedora-s390x
> 
> In file included from /usr/include/c++/11/string:40,
>                  from ../../binutils-gdb/gdb/../gdbsupport/ptid.h:36,
>                  from ../../binutils-gdb/gdb/../gdbsupport/common-defs.h:198,
>                  from ../../binutils-gdb/gdb/defs.h:28,
>                  from ../../binutils-gdb/gdb/debuginfod-support.c:19:
> In static member function ‘static constexpr const char_type* std::char_traits<char>::find(const char_type*, std::size_t, const char_type&)’,
>     inlined from ‘constexpr std::basic_string_view<_CharT, _Traits>::size_type std::basic_string_view<_CharT, _Traits>::find(_CharT, std::basic_string_view<_CharT, _Traits>::size_type) const [with _CharT = char; _Traits = std::char_traits<char>]’ at /usr/include/c++/11/bits/string_view.tcc:87:41,
>     inlined from ‘constexpr std::basic_string_view<_CharT, _Traits>::size_type std::basic_string_view<_CharT, _Traits>::find_first_of(_CharT, std::basic_string_view<_CharT, _Traits>::size_type) const [with _CharT = char; _Traits = std::char_traits<char>]’ at /usr/include/c++/11/string_view:431:26,
>     inlined from ‘bool debuginfod_is_enabled()’ at ../../binutils-gdb/gdb/debuginfod-support.c:194:33:
> /usr/include/c++/11/bits/char_traits.h:413:62: error: ‘void* __builtin_memchr(const void*, int, long unsigned int)’ specified bound 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Werror=stringop-overread]
>   413 |         return static_cast<const char_type*>(__builtin_memchr(__s, __a, __n));
>       |                                              ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
> 

This is really weird. I don't know why, but for some reason g++ (GCC)
11.2.1 20220127 (Red Hat 11.2.1-9) on s390x seems convinced the string
might be of SIZE_MAX lenght. And so complains because the length of an
array can only be PTRDIFF_MAX. The following "fixes" it:

diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
index 4ce2e786..d4f8a55c 100644
--- a/gdb/debuginfod-support.c
+++ b/gdb/debuginfod-support.c
@@ -190,7 +190,10 @@ debuginfod_is_enabled ()
          size_t off = url_view.find_first_not_of (' ');
          if (off == gdb::string_view::npos)
            break;
-         url_view = url_view.substr (off);
+         /* Use PTRDIFF_MAX otherwise g++ might (wrongly) believe
+            the string might be SIZE_MAX and warn for specified bound
+            exceeding maximum object size on find.  */
+         url_view = url_view.substr (off, PTRDIFF_MAX);
          off = url_view.find_first_of (' ');
          gdb_printf
            (_("  <%ps>\n"),

Is that a reasonable workaround?

Thanks,

Mark