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Fix completion related libstdc++ assert when using -D_GLIBCXX_DEBUG

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This commit fixes a libstdc++ assertion failure encountered when
running gdb.base/completion.exp.  In order to see this problem,
GDB must be built with the follow CFLAGS and CXXFLAGS as part
of the configure line:

  CFLAGS='-D_GLIBCXX_DEBUG' CXXFLAGS='-D_GLIBCXX_DEBUG'

(Also, this problem was encountered using Fedora rawhide.  It might
not be reproducible in Fedora versions prior to Fedora 34.)

Using the gdb.base/completion.exp test program, the problem can be
observed as follows:

[kev@rawhide-1 gdb]$ ./gdb -q testsuite/outputs/gdb.base/completion/completion
Reading symbols from testsuite/outputs/gdb.base/completion/completion...
(gdb) start
Temporary breakpoint 1 at 0x401179: file ../../worktree-master/gdb/testsuite/gdb.base/break.c, line 43.
Starting program: testsuite/outputs/gdb.base/completion/completion

Temporary breakpoint 1, main (argc=1, argv=0x7fffffffd718, envp=0x7fffffffd728) at ../../worktree-master/gdb/testsuite/gdb.base/break.c:43
43	    if (argc == 12345) {  /* an unlikely value < 2^16, in case uninited */ /* set breakpoint 6 here */
(gdb) p <TAB>/usr/include/c++/11/string_view:211: 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.
Aborted (core dumped)

(Note that I added "<TAB>" to make it clear where the tab key was
pressed.)

gdb/ChangeLog:

	* ada-lang.c (ada_fold_name): Check for non-empty string prior
	to accessing it.
	(ada_lookup_name_info): Likewise.
This commit is contained in:
Kevin Buettner 2021-02-12 17:53:51 -07:00
parent afadac6170
commit 6a780b6766
2 changed files with 8 additions and 2 deletions
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4
gdb/ada-lang.c
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@ -980,7 +980,7 @@ ada_fold_name (gdb::string_view name)
int len = name.size ();
GROW_VECT (fold_buffer, fold_buffer_size, len + 1);
if (name[0] == '\'')
if (!name.empty () && name[0] == '\'')
{
strncpy (fold_buffer, name.data () + 1, len - 2);
fold_buffer[len - 2] = '\000';
@ -13650,7 +13650,7 @@ ada_lookup_name_info::ada_lookup_name_info (const lookup_name_info &lookup_name)
{
gdb::string_view user_name = lookup_name.name ();
if (user_name[0] == '<')
if (!user_name.empty () && user_name[0] == '<')
{
if (user_name.back () == '>')
m_encoded_name