Hello,

I recently got really frustrated that I couldn't set thread-specific
breakpoints when using the "*<addr>" linespec location. The reason for
this has been discussed already, but I can't seem to find the thread in
the archives. Basically, the "*<addr>" notation treats <addr> as an
expression and the expression parser emits a parse error if you add
'thread xxx' to the line.

This works for breakpoint conditions because "if" is special-cased in
the expression parsers to stop the parsing. At least for C(++), there
can't be any expression typed in GDB that would contain the "if"
reserved keyword, so handling it as a stop condition in the expression
parser is OK. That can't be done for "thread" because it's a valid
language identifier.

The attached patch doesn't try to solve the parsing issue, but it simply
adds a 'threadnum' command that one can use to (un)set the thread of a
particular breakpoint. I'm not sure about the command name, because it
will conflict with the thread command. Suggestions appreciated. I also
wonder if new CLI commands should be added only in the 'cli' subdir?

Of course, the patch is missing a doco part and maybe testsuite
coverage, but I thought I'd first ask if there's interest for this or if
I missed an existing way to do it (seems quite surprising that this
doesn't already exist).
Maybe the alternate approach of adding a $thread variable to use in bp
conditions ( http://www.sourceware.org/ml/gdb/2006-02/msg00017.html )
should be implemented instead ?

Fred.