By default, when you ask to collect a char * at a tracepoint, only the
numeric address is collected, which is a problem if you really want the
string that the char * is pointing to. This patch adds a /s option to
the collect action that will dereference character pointers and collect
the bytes up to the first zero, just as the familiar print command
does. You can optionally add a limit to the collect, so for instance
"collect/s80 mystring" collects a maximum of 80 characters.
While conceptually simple, we need a new agent bytecode to make this
work (writing a loop using existing bytecodes doesn't let us check that
we're running off the edge of valid memory), and a support flag so that
users get informed if the target doesn't support string collection.
If you're having a sense of dejavu about all this :-) , there was a
discussion of syntax last year, starting from
http://sourceware.org/ml/gdb/2010-06/msg00018.html . I ended up
following Michael Snyder's suggested syntax.
Stan
stan@codesourcery.com
2011-10-03 Stan Shebs <stan@codesourcery.com>
String collection for tracepoints.
* common/ax.def (tracenz): New bytecode.
* ax-gdb.h (string_kludge): Declare.
* ax-gdb.c: Include valprint.h and c-lang.h.
(string_kludge): New global.
(gen_traced_pop): Add string case.
(agent_command): Add string case.
* tracepoint.h (decode_agent_options): Declare.
* tracepoint.c (decode_agent_options): New function.
(validate_actionline): Call it.
(encode_actions_1): Ditto.
* target.h (struct target_ops): New method to_supports_string_tracing.
(target_supports_string_tracing): New macro.
* target.c (update_current_target): Add to_supports_string_tracing.
* remote.c (struct remote_state): New field string_tracing.
(remote_string_tracing_feature): New function.
(remote_protocol_features): New feature tracenz.
(remote_supports_string_tracing): New function.
(init_remote_ops): Set to_supports_string_tracing.
* tracepoint.c (agent_mem_read_string): New function.
(eval_agent_expr): Call it for tracenz.
* server.c (handle_query): Report support for tracenz.
* gdb.texinfo (Tracepoint Action Lists): Document collect/s.
* agentexpr.texi: Describe tracenz.
* gdb.trace/collection.c: Add code using strings.
* gdb.trace/collection.exp: Add tests of string collection.
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: tstr-patch-1
URL: <http://sourceware.org/pipermail/gdb-patches/attachments/20111003/445e4b35/attachment.ksh>