From: Simon Marchi <simon.marchi@polymtl.ca>
To: gdb-patches@sourceware.org
Subject: [PATCH] gdbsupport: fix path_join crash with -std=c++17 and -D_GLIBCXX_DEBUG
Date: Wed, 4 May 2022 10:18:40 -0400 [thread overview]
Message-ID: <20220504141840.1269433-1-simon.marchi@polymtl.ca> (raw)
When building GDB with -std=c++17 and -D_GLIBCXX_DEBUG=1, I get:
$ ./gdb -nx --data-directory=data-directory -q -ex "maint selftest path_join"
/usr/include/c++/11.2.0/string_view:233: constexpr const value_type& std::basic_string_view<_CharT, _Traits>::operator[](std::basic_string_view<_CharT, _Traits>::size_type) const [with _CharT = char; _Traits = std::char_traits<char>; std::basic_string_view<_CharT, _Traits>::const_reference = const char&; std::basic_string_view<_CharT, _Traits>::size_type = long unsigned int]: Assertion '__pos < this->_M_len' failed.
The problem is that we're passing an empty string_view to
IS_ABSOLUTE_PATH. IS_ABSOLUTE_PATH accesses [0] on that string_view,
which is out-of-bounds.
The reason this is not seen with -std less than c++17 is that our local
copy of string_view (used with C++ < 17) does not have the assert in
operator[], as that wouldn't work in a constexpr method:
https://gitlab.com/gnutools/binutils-gdb/-/blob/5890af36e5112bcbb8d7555e63570f68466e6944/gdbsupport/gdb_string_view.h#L180
IS_ABSOLUTE_PATH is normally used with null-terminated string. It's
fine to pass an empty null-terminated string to IS_ABSOLUTE_PATH,
because index 0 in such a string is valid. But not with an empty
string_view.
Fix that by avoiding the "call" to IS_ABSOLUTE_PATH if the string_view
is empty.
Change-Id: Idf4df961b63f513b3389235e93814c02b89ea32e
---
gdbsupport/pathstuff.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gdbsupport/pathstuff.cc b/gdbsupport/pathstuff.cc
index 5b5a8eea9047..af10c6ebd2e8 100644
--- a/gdbsupport/pathstuff.cc
+++ b/gdbsupport/pathstuff.cc
@@ -200,7 +200,7 @@ path_join (gdb::array_view<const gdb::string_view> paths)
const gdb::string_view path = paths[i];
if (i > 0)
- gdb_assert (!IS_ABSOLUTE_PATH (path));
+ gdb_assert (path.empty () || !IS_ABSOLUTE_PATH (path));
if (!ret.empty () && !IS_DIR_SEPARATOR (ret.back ()))
ret += '/';
base-commit: 5890af36e5112bcbb8d7555e63570f68466e6944
--
2.36.0
next reply other threads:[~2022-05-04 14:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-04 14:18 Simon Marchi [this message]
2022-05-19 12:08 ` Simon Marchi
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