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27.17 GDB/MI Tracepoint Commands

The commands defined in this section implement MI support for tracepoints. For detailed introduction, see Tracepoints.

The -trace-find Command

Synopsis

 -trace-find mode [parameters…]

Find a trace frame using criteria defined by mode and parameters. The following table lists permissible modes and their parameters. For details of operation, see tfind.

none

No parameters are required. Stops examining trace frames.

frame-number

An integer is required as parameter. Selects tracepoint frame with that index.

tracepoint-number

An integer is required as parameter. Finds next trace frame that corresponds to tracepoint with the specified number.

pc

An address is required as parameter. Finds next trace frame that corresponds to any tracepoint at the specified address.

pc-inside-range

Two addresses are required as parameters. Finds next trace frame that corresponds to a tracepoint at an address inside the specified range. Both bounds are considered to be inside the range.

pc-outside-range

Two addresses are required as parameters. Finds next trace frame that corresponds to a tracepoint at an address outside the specified range. Both bounds are considered to be inside the range.

line

Line specification is required as parameter. See Specify Location. Finds next trace frame that corresponds to a tracepoint at the specified location.

If ‘none’ was passed as mode, the response does not have fields. Otherwise, the response may have the following fields:

found

This field has either ‘0’ or ‘1’ as the value, depending on whether a matching tracepoint was found.

traceframe

The index of the found traceframe. This field is present iff the ‘found’ field has value of ‘1’.

tracepoint

The index of the found tracepoint. This field is present iff the ‘found’ field has value of ‘1’.

frame

The information about the frame corresponding to the found trace frame. This field is present only if a trace frame was found. See GDB/MI Frame Information, for description of this field.

GDB Command

The corresponding GDB command is ‘tfind’.

-trace-define-variable

Synopsis

 -trace-define-variable name [ value ]

Create trace variable name if it does not exist. If value is specified, sets the initial value of the specified trace variable to that value. Note that the name should start with the ‘$’ character.

GDB Command

The corresponding GDB command is ‘tvariable’.

The -trace-frame-collected Command

Synopsis

 -trace-frame-collected
    [--var-print-values var_pval]
    [--comp-print-values comp_pval]
    [--registers-format regformat]
    [--memory-contents]

This command returns the set of collected objects, register names, trace state variable names, memory ranges and computed expressions that have been collected at a particular trace frame. The optional parameters to the command affect the output format in different ways. See the output description table below for more details.

The reported names can be used in the normal manner to create varobjs and inspect the objects themselves. The items returned by this command are categorized so that it is clear which is a variable, which is a register, which is a trace state variable, which is a memory range and which is a computed expression.

For instance, if the actions were

collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
collect *(int*)0xaf02bef0@40

the object collected in its entirety would be myVar. The object myArray would be partially collected, because only the element at index myIndex would be collected. The remaining objects would be computed expressions.

An example output would be:

(gdb)
-trace-frame-collected
^done,
  explicit-variables=[{name="myVar",value="1"}],
  computed-expressions=[{name="myArray[myIndex]",value="0"},
                        {name="myObj.field",value="0"},
                        {name="myPtr->field",value="1"},
                        {name="myCount + 2",value="3"},
                        {name="$tvar1 + 1",value="43970027"}],
  registers=[{number="0",value="0x7fe2c6e79ec8"},
             {number="1",value="0x0"},
             {number="2",value="0x4"},
             ...
             {number="125",value="0x0"}],
  tvars=[{name="$tvar1",current="43970026"}],
  memory=[{address="0x0000000000602264",length="4"},
          {address="0x0000000000615bc0",length="4"}]
(gdb)

Where:

explicit-variables

The set of objects that have been collected in their entirety (as opposed to collecting just a few elements of an array or a few struct members). For each object, its name and value are printed. The --var-print-values option affects how or whether the value field is output. If var_pval is 0, then print only the names; if it is 1, print also their values; and if it is 2, print the name, type and value for simple data types, and the name and type for arrays, structures and unions.

computed-expressions

The set of computed expressions that have been collected at the current trace frame. The --comp-print-values option affects this set like the --var-print-values option affects the explicit-variables set. See above.

registers

The registers that have been collected at the current trace frame. For each register collected, the name and current value are returned. The value is formatted according to the --registers-format option. See the -data-list-register-values command for a list of the allowed formats. The default is ‘x’.

tvars

The trace state variables that have been collected at the current trace frame. For each trace state variable collected, the name and current value are returned.

memory

The set of memory ranges that have been collected at the current trace frame. Its content is a list of tuples. Each tuple represents a collected memory range and has the following fields:

address

The start address of the memory range, as hexadecimal literal.

length

The length of the memory range, as decimal literal.

contents

The contents of the memory block, in hex. This field is only present if the --memory-contents option is specified.

GDB Command

There is no corresponding GDB command.

Example

-trace-list-variables

Synopsis

 -trace-list-variables

Return a table of all defined trace variables. Each element of the table has the following fields:

name

The name of the trace variable. This field is always present.

initial

The initial value. This is a 64-bit signed integer. This field is always present.

current

The value the trace variable has at the moment. This is a 64-bit signed integer. This field is absent iff current value is not defined, for example if the trace was never run, or is presently running.

GDB Command

The corresponding GDB command is ‘tvariables’.

Example

(gdb)
-trace-list-variables
^done,trace-variables={nr_rows="1",nr_cols="3",
hdr=[{width="15",alignment="-1",col_name="name",colhdr="Name"},
     {width="11",alignment="-1",col_name="initial",colhdr="Initial"},
     {width="11",alignment="-1",col_name="current",colhdr="Current"}],
body=[variable={name="$trace_timestamp",initial="0"}
      variable={name="$foo",initial="10",current="15"}]}
(gdb)

-trace-save

Synopsis

 -trace-save [-r ] filename

Saves the collected trace data to filename. Without the ‘-r’ option, the data is downloaded from the target and saved in a local file. With the ‘-r’ option the target is asked to perform the save.

GDB Command

The corresponding GDB command is ‘tsave’.

-trace-start

Synopsis

 -trace-start

Starts a tracing experiments. The result of this command does not have any fields.

GDB Command

The corresponding GDB command is ‘tstart’.

-trace-status

Synopsis

 -trace-status

Obtains the status of a tracing experiment. The result may include the following fields:

supported

May have a value of either ‘0’, when no tracing operations are supported, ‘1’, when all tracing operations are supported, or ‘file’ when examining trace file. In the latter case, examining of trace frame is possible but new tracing experiement cannot be started. This field is always present.

running

May have a value of either ‘0’ or ‘1’ depending on whether tracing experiement is in progress on target. This field is present if ‘supported’ field is not ‘0’.

stop-reason

Report the reason why the tracing was stopped last time. This field may be absent iff tracing was never stopped on target yet. The value of ‘request’ means the tracing was stopped as result of the -trace-stop command. The value of ‘overflow’ means the tracing buffer is full. The value of ‘disconnection’ means tracing was automatically stopped when GDB has disconnected. The value of ‘passcount’ means tracing was stopped when a tracepoint was passed a maximal number of times for that tracepoint. This field is present if ‘supported’ field is not ‘0’.

stopping-tracepoint

The number of tracepoint whose passcount as exceeded. This field is present iff the ‘stop-reason’ field has the value of ‘passcount’.

frames
frames-created

The ‘frames’ field is a count of the total number of trace frames in the trace buffer, while ‘frames-created’ is the total created during the run, including ones that were discarded, such as when a circular trace buffer filled up. Both fields are optional.

buffer-size
buffer-free

These fields tell the current size of the tracing buffer and the remaining space. These fields are optional.

circular

The value of the circular trace buffer flag. 1 means that the trace buffer is circular and old trace frames will be discarded if necessary to make room, 0 means that the trace buffer is linear and may fill up.

disconnected

The value of the disconnected tracing flag. 1 means that tracing will continue after GDB disconnects, 0 means that the trace run will stop.

trace-file

The filename of the trace file being examined. This field is optional, and only present when examining a trace file.

GDB Command

The corresponding GDB command is ‘tstatus’.

-trace-stop

Synopsis

 -trace-stop

Stops a tracing experiment. The result of this command has the same fields as -trace-status, except that the ‘supported’ and ‘running’ fields are not output.

GDB Command

The corresponding GDB command is ‘tstop’.


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