gdb/python: Add gdb.InferiorThread.details attribute

This adds a new read-only attribute gdb.InferiorThread.details, this
attribute contains a string, the results of target_extra_thread_info
for the thread, or None, if target_extra_thread_info returns nullptr.

As the string returned by target_extra_thread_info is unstructured,
this attribute is only really useful for echoing straight through to
the user, but, if a user wants to write a command that displays the
same, or a similar 'Thread Id' to the one seen in 'info threads', then
they need access to this string.

Given that the string produced by target_extra_thread_info varies by
target, there's only minimal testing of this attribute, I check that
the attribute can be accessed, and that the return value is either
None, or a string.

2 files changed, 19 insertions, 0 deletions

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 504eb66..f7f5f7a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -3629,6 +3629,7 @@ Thread 1 "main" received signal SIGINT, Interrupt.
 @end smallexample
 
 @table @code
+@anchor{info_threads}
 @kindex info threads
 @item info threads @r{[}@var{thread-id-list}@r{]}
 
@@ -42719,6 +42720,7 @@ encoded).  @value{GDBN} will continue to supply the values of symbols
 
 @xref{Tracepoint Packets}.
 
+@anchor{qThreadExtraInfo}
 @item qThreadExtraInfo,@var{thread-id}
 @cindex thread attributes info, remote request
 @cindex @samp{qThreadExtraInfo} packet
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index c1a3f5f..4d9e77b 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -3574,6 +3574,23 @@ The inferior this thread belongs to.  This attribute is represented as
 a @code{gdb.Inferior} object.  This attribute is not writable.
 @end defvar
 
+@defvar InferiorThread.details
+A string containing target specific thread state information.  The
+format of this string varies by target.  If there is no additional
+state information for this thread, then this attribute contains
+@code{None}.
+
+For example, on a @sc{gnu}/Linux system, a thread that is in the
+process of exiting will return the string @samp{Exiting}.  For remote
+targets the @code{details} string will be obtained with the
+@samp{qThreadExtraInfo} remote packet, if the target supports it
+(@pxref{qThreadExtraInfo,,@samp{qThreadExtraInfo}}).
+
+@value{GDBN} displays the @code{details} string as part of the
+@samp{Target Id} column, in the @code{info threads} output
+(@pxref{info_threads,,@samp{info threads}}).
+@end defvar
+
 A @code{gdb.InferiorThread} object has the following methods:
 
 @defun InferiorThread.is_valid ()