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From: Simon Marchi <simark@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] gdbsupport: fix path_join crash with -std=c++17 and -D_GLIBCXX_DEBUG Date: Thu, 19 May 2022 12:08:45 +0000 (GMT) [thread overview] Message-ID: <20220519120845.332A5384B83F@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=02646f1960a53e50c05218725cbf63098bee5bbe commit 02646f1960a53e50c05218725cbf63098bee5bbe Author: Simon Marchi <simon.marchi@polymtl.ca> Date: Wed May 4 10:10:25 2022 -0400 gdbsupport: fix path_join crash with -std=c++17 and -D_GLIBCXX_DEBUG 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 Diff: --- gdbsupport/pathstuff.cc | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gdbsupport/pathstuff.cc b/gdbsupport/pathstuff.cc index 5b5a8eea904..af10c6ebd2e 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 += '/';
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