Hi Lianbo,

thanks for writing the patch!

-----Original Message-----
> Currently, crash may generate core dump and print the following
> error when running the commands "l panic" or "p" TAB completion.

I have still not reproduce this with upstream sources, it looks like a
combination of build flags is needed, but not sure about the minimum set.
And I think that, more exactly, the gdb list command or tab-completion of
symbols cause it, so please modify like this:
---
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()).

Please add this here:
---
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@redhat.com>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> ---
>  gdb-10.2.patch | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/gdb-10.2.patch b/gdb-10.2.patch
> index 1332b6638028..16165839b360 100644
> --- a/gdb-10.2.patch
> +++ b/gdb-10.2.patch
> @@ -1591,3 +1591,32 @@
>     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.size () > 0 && name[0] == '\'')
> +     {
> +       strncpy (fold_buffer, name.data () + 1, len - 2);
> +       fold_buffer[len - 2] = '\000';
> +@@ -1006,7 +1006,7 @@ ada_fold_name (gdb::string_view name)
> +     {
> +       int i;
> +
> +-      for (i = 0; i <= len; i += 1)
> ++      for (i = 0; i < len; i++)
> +         fold_buffer[i] = tolower (name[i]);

According to 2ccee230f830 ("Fix off-by-one error in ada_fold_name"),
please add this:

+      fold_buffer[i] = '\0';

We should backport gdb patches as they are if possible, for future backports.

> +     }
> +
> +@@ -13596,7 +13596,7 @@ 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.size () > 0 && user_name[0] == '<')
> +     {
> +       if (user_name.back () == '>')
> +     m_encoded_name
> --
> 2.20.1