From 947f7597788b646683cb37b2833ed1844ce7d1bc Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Mon, 6 Jul 2020 09:54:43 +0200 Subject: [PATCH] [gdb/tui,c++17] Fix NULL string_view in tui_partial_win_by_name 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" Aborted (core dumped) $ ... with this backtrace at the abort: ... \#0 0x0000000000438db0 in std::char_traits::length (__s=0x0) at /usr/include/c++/9/bits/char_traits.h:335 \#1 0x000000000043b72e in std::basic_string_view >::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 PR tui/26205 * tui/tui-win.c (tui_partial_win_by_name): Don't test for NULL name. --- gdb/ChangeLog | 5 +++++ gdb/tui/tui-win.c | 23 ++++++++++------------- 2 files changed, 15 insertions(+), 13 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 21dc3e2b2f9..b802641c9d2 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2020-07-06 Tom de Vries + + PR tui/26205 + * tui/tui-win.c (tui_partial_win_by_name): Don't test for NULL name. + 2020-07-05 Tom de Vries PR build/26187 diff --git a/gdb/tui/tui-win.c b/gdb/tui/tui-win.c index 336571f158e..f906b0dc4fe 100644 --- a/gdb/tui/tui-win.c +++ b/gdb/tui/tui-win.c @@ -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; } } -- 2.30.2