gdb remote protocol breakpoints (Z0 command)

David Taylor
Thu Jun 19 14:44:00 GMT 2014

In the manual the Z0 (insert memory breakpoint) command is summarized


Now, cond_list 'is comprised of a series of expressions, concatenated
without separators.  Each expression has the following form:

    X len,expr

len is the length of the bytecode expression and expr is the actual
conditional expression in bytecode form.

That part is fine.  Most of the time when I want a conditional
breakpoint, the expression is expressible in bytecode form.  (In fact,
while I won't attest that they've always been so expressible, I don't
recall any that weren't so expressible).

But, it then goes on to describe cmd_list in similar terms.

There are many things you might want to do at a breakpoint that lack
bytecode operators.  Just for starters,

    . there is no bytecode operator for setting memory

    . there is no bytecode operator for setting registers

    . there is no bytecode operator for calling arbitrary functions

    . there is no 'continue' option (as in: ``after performing the
    requested commands, continue the current thread'')

There are other capabilities that I would like as well, but without the
four mentioned above, I don't consider it very useful at all.

Has anyone else thought about these issuses and possibly sketched out
extensions to allow such capabilities?

[The 'continue' command would likely be an extension to the Z0 command,
the others would likely be extensions to the bytecode language.]

If we (EMC) were to do something in our gdb and/or remote stub, I would
want it to be compatible with what others are doing / thinking of doing.


David Taylor
dtaylor at emc dot com

More information about the Gdb mailing list