[Crash-utility] [PATCH v2] GDB: fix completion related libstdc++ assert

[Lianbo Jiang]

Currently crash built with some specific flags (-D_GLIBCXX_ASSERTIONS
and etc.) may abort and print the following error when running the gdb
list command or tab-completion of symbols. For example:

crash> l panic
/usr/include/c++/11/string_view:234: ...
Aborted (core dumped)

crash> p "TAB completion"
crash> p /usr/include/c++/11/string_view:234: ...
Aborted (core dumped)

When the name string is null(the length of name is zero), there are
multiple places where array access is out of bounds in the gdb/ada-lang.c
(see ada_fold_name() and ada_lookup_name_info()).

The patch backports these gdb patches:
6a780b676637 ("Fix completion related libstdc++ assert when using -D_GLIBCXX_DEBUG")
2ccee230f830 ("Fix off-by-one error in ada_fold_name")

Signed-off-by: Lianbo Jiang <lijiang at redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
---
 gdb-10.2.patch | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/gdb-10.2.patch b/gdb-10.2.patch
index 1332b6638028..f5e4c06e6f97 100644
--- a/gdb-10.2.patch
+++ b/gdb-10.2.patch
@@ -1591,3 +1591,34 @@
    max += 2;
    limit = cols / max;
    if (limit != 1 && (limit * max == cols))
+--- gdb-10.2/gdb/ada-lang.c.orig
++++ gdb-10.2/gdb/ada-lang.c
+@@ -997,7 +997,7 @@ 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';
+@@ -1006,8 +1006,9 @@ ada_fold_name (gdb::string_view name)
+     {
+       int i;
+ 
+-      for (i = 0; i <= len; i += 1)
++      for (i = 0; i < len; i += 1)
+         fold_buffer[i] = tolower (name[i]);
++      fold_buffer[i] = '\0';
+     }
+ 
+   return fold_buffer;
+@@ -13596,7 +13597,7 @@ 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
-- 
2.20.1