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[gdb/tui,c++17] Fix NULL string_view in tui_partial_win_by_name

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When building gdb with CFLAGS=-std=gnu17 and CXXFLAGS=-std=gnu++17 and running
test-case gdb.tui/new-layout.exp, we run into:
...
UNRESOLVED: gdb.tui/new-layout.exp: left window box after shrink (ll corner)
FAIL: gdb.tui/new-layout.exp: right window box after shrink (ll corner)
...

In a minimal form, we run into an abort when issuing a winheight command:
...
$ gdb -tui -ex "winheight src - 5"
   <tui stuff>
Aborted (core dumped)
$
...
with this backtrace at the abort:
...
\#0  0x0000000000438db0 in std::char_traits<char>::length (__s=0x0)
     at /usr/include/c++/9/bits/char_traits.h:335
\#1  0x000000000043b72e in std::basic_string_view<char, \
   std::char_traits<char> >::basic_string_view (this=0x7fffffffd4f0, \
   __str=0x0) at /usr/include/c++/9/string_view:124
\#2  0x000000000094971b in tui_partial_win_by_name (name="src")
     at src/gdb/tui/tui-win.c:663
...
due to a NULL comparison which constructs a string_view object from NULL:
...
   657  /* Answer the window represented by name.  */
   658  static struct tui_win_info *
   659  tui_partial_win_by_name (gdb::string_view name)
   660  {
   661    struct tui_win_info *best = nullptr;
   662
   663    if (name != NULL)
...

In gdbsupport/gdb_string_view.h, we either use:
- gdb's copy of libstdc++-v3/include/experimental/string_view, or
- the standard implementation of string_view, when built with C++17 or later
  (which in gcc's case comes from libstdc++-v3/include/std/string_view)

In the first case, there's support for constructing a string_view from a NULL
pointer:
...
      /*constexpr*/ basic_string_view(const _CharT* __str)
      : _M_len{__str == nullptr ? 0 : traits_type::length(__str)},
        _M_str{__str}
      { }
...
but in the second case, there's not:
...
      __attribute__((__nonnull__)) constexpr
      basic_string_view(const _CharT* __str) noexcept
      : _M_len{traits_type::length(__str)},
        _M_str{__str}
      { }
...

Fix this by removing the NULL comparison altogether.

Build on x86_64-linux with CFLAGS=-std=gnu17 and CXXFLAGS=-std=gnu++17, and
tested.

gdb/ChangeLog:

2020-07-06  Tom de Vries  <tdevries@suse.de>

	PR tui/26205
	* tui/tui-win.c (tui_partial_win_by_name): Don't test for NULL name.
This commit is contained in:
Tom de Vries 2020-07-06 09:54:43 +02:00
parent ddb43bab17
commit 947f759778
2 changed files with 15 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
gdb/ChangeLog
View File

@ -1,3 +1,8 @@
2020-07-06 Tom de Vries <tdevries@suse.de>
PR tui/26205
* tui/tui-win.c (tui_partial_win_by_name): Don't test for NULL name.
2020-07-05 Tom de Vries <tdevries@suse.de>
PR build/26187

23
gdb/tui/tui-win.c
View File

@ -660,21 +660,18 @@ tui_partial_win_by_name (gdb::string_view name)
{
struct tui_win_info *best = nullptr;
if (name != NULL)
for (tui_win_info *item : all_tui_windows ())
{
for (tui_win_info *item : all_tui_windows ())
{
const char *cur_name = item->name ();
const char *cur_name = item->name ();
if (name == cur_name)
return item;
if (startswith (cur_name, name))
{
if (best != nullptr)
error (_("Window name \"%*s\" is ambiguous"),
(int) name.size (), name.data ());
best = item;
}
if (name == cur_name)
return item;
if (startswith (cur_name, name))
{
if (best != nullptr)
error (_("Window name \"%*s\" is ambiguous"),
(int) name.size (), name.data ());
best = item;
}
}