[PING] [PATCH v2] Fix -var-update for registers in frames 1 and up

[Don Breazeal <donb at codesourcery dot com>]

Hi.  This patch has been in the queue for quite a while.  ping.
Thanks!
--Don

>>>>
>>>> On 6/20/2016 8:31 AM, Don Breazeal wrote:
>>>>> On 6/13/2016 2:54 PM, Don Breazeal wrote:
>>>>>> This is an updated version of a patch to fix access to registers
>>>>>> for frames other than the current frame via var-update.  The piece
>>>>>> of the patch affecting GDB proper has been completely re-written.
>>>>>> It changes the initialization of varobj->root->frame in varobj_create
>>>>>> so that existing mechanisms (with minimal changes) select the correct
>>>>>> frame and provide correct register values from -var-update.
>>>>>>
>>>>>> In addition, the new test for this functionality has been expanded
>>>>>> to cover an analogous case using floating variable objects, and
>>>>>> several tests have been updated to account for the fact that with
>>>>>> the new initialization, -var-create and -var-list-children now
>>>>>> provide a thread-id field where previously they didn't.
>>>>>>
>>>>>> Thanks
>>>>>> --Don
>>>>>>
>>>>>> ------------
>>>>>> This patch fixes a problem with using the MI -var-update command
>>>>>> to access the values of registers in frames other than the current
>>>>>> frame.  The patch includes a test that demonstrates the problem:
>>>>>>
>>>>>> * run so there are several frames on the stack
>>>>>> * create a fixed varobj for $pc in each frame, #'s 1 and above
>>>>>> * step one instruction, to modify the value of $pc
>>>>>> * call -var-update for each of the previously created varobjs
>>>>>>   to verify that they are not reported as having changed.
>>>>>>
>>>>>> Without the patch, the -var-update command reported that $pc for all
>>>>>> frames 1 and above had changed to the value of $pc in frame 0.
>>>>>>
>>>>>> When a varobj is created by -var-create, varobj->root->frame should
>>>>>> be set to specified frame.  Then for a subsequent -var-update,
>>>>>> varobj.c:check_scope can use varobj->root->frame to select the
>>>>>> right frame based on the type of varobj.
>>>>>>
>>>>>> The problem is that for register expressions varobj->root->frame is not
>>>>>> set correctly.  This frame tracking is done using the global
>>>>>> 'innermost_block' which is set in the various parser files (for example
>>>>>> c-exp.y).  However, this is not set for register expressions.
>>>>>>
>>>>>> The fix is to change the initialization of innermost_block in
>>>>>> varobj_create from NULL to the global block, as returned by
>>>>>> block_global_block.  Then varobj_create sets varobj->root->frame
>>>>>> for register varobjs, and value_of_root_1 can check for the
>>>>>> global block when determining whether the variable is in-scope
>>>>>> and select the frame appropriately.
>>>>>>
>>>>>> A side-effect of this change is that for register varobjs and some
>>>>>> global variable varobjs, the output of -var-create now includes the
>>>>>> thread-id field.  The rationale for this is as follow: if we ask for a
>>>>>> particular expression in a particular frame, that implies a particular
>>>>>> thread.  Thus including the thread-id is correct behavior, and the
>>>>>> test results have been updated accordingly.
>>>>>>
>>>>>> In addition there is a new test, gdb.mi/mi-frame-regs.exp, which
>>>>>> performs the test described in the bullet list above as well as a
>>>>>> similar test using a floating variable object to represent $pc.
>>>>>>
>>>>>> We attempted a couple alternative solutions:
>>>>>> * a special case in varobj_update to select the frame was not ideal
>>>>>>   because it didn't use the existing mechanisms to select the frame.
>>>>>> * setting innermost_block in write_dollar_variable had side-effects
>>>>>>   in the CLI that would have required special case code.
>>>>>>
>>>>>> Tested on x86_64 Linux native, no regressions.
>>>>>>
>>>>>> gdb/testsuite/ChangeLog:
>>>>>> 2016-06-13  Don Breazeal  <dbreazea@my.domain.org>
>>>>>>
>>>>>> 	* gdb.ada/mi_interface.exp: Add thread-id field to expected
>>>>>> 	output of -var-create and -var-list-children.
>>>>>> 	* gdb.ada/mi_var_array.exp: Add thread-id field to expected
>>>>>> 	output of -var-list-children.
>>>>>> 	* gdb.mi/mi-break.exp (test_error): Add thread-id field to
>>>>>> 	expected output of -var-create.
>>>>>> 	* gdb.mi/mi-frame-regs.exp: New test script.
>>>>>> 	* gdb.mi/mi-var-cmd.exp: Add thread-id field to expected
>>>>>> 	output of -var-create.
>>>>>> 	* gdb.mi/mi-var-create-rtti.exp: Likewise.
>>>>>>
>>>>>> gdb/ChangeLog:
>>>>>> 2016-06-13  Don Breazeal  <donb@codesourcery.com>
>>>>>> 	    Andrew Burgess <andrew.burgess@embecosm.com>
>>>>>>
>>>>>> 	* varobj.c (varobj_create): Initialize innermost_block to
>>>>>> 	the global block instead of NULL.
>>>>>> 	(new_root_variable): Initialize the thread_id and next
>>>>>> 	fields.
>>>>>> 	(value_of_root_1): Set within_scope if the variable's
>>>>>> 	valid_block field is the global block.
>>>>>>
>>>>>> ---
>>>>>>  gdb/testsuite/gdb.ada/mi_interface.exp      |   4 +-
>>>>>>  gdb/testsuite/gdb.ada/mi_var_array.exp      |   2 +-
>>>>>>  gdb/testsuite/gdb.mi/mi-break.exp           |   2 +-
>>>>>>  gdb/testsuite/gdb.mi/mi-frame-regs.exp      | 183 ++++++++++++++++++++++++++++
>>>>>>  gdb/testsuite/gdb.mi/mi-var-cmd.exp         |   4 +-
>>>>>>  gdb/testsuite/gdb.mi/mi-var-create-rtti.exp |   2 +-
>>>>>>  gdb/varobj.c                                |   8 +-
>>>>>>  7 files changed, 196 insertions(+), 9 deletions(-)
>>>>>>
>>>>>> diff --git a/gdb/testsuite/gdb.ada/mi_interface.exp b/gdb/testsuite/gdb.ada/mi_interface.exp
>>>>>> index 6000ec8..b948cd5 100644
>>>>>> --- a/gdb/testsuite/gdb.ada/mi_interface.exp
>>>>>> +++ b/gdb/testsuite/gdb.ada/mi_interface.exp
>>>>>> @@ -44,9 +44,9 @@ mi_continue_to_line \
>>>>>>      "stop at start of main Ada procedure"
>>>>>>  
>>>>>>  mi_gdb_test "-var-create ggg1 * ggg1" \
>>>>>> -    "\\^done,name=\"ggg1\",numchild=\"1\",value=\"{...}\",type=\"<ref> pck.gadatatype\",has_more=\"0\"" \
>>>>>> +    "\\^done,name=\"ggg1\",numchild=\"1\",value=\"{...}\",type=\"<ref> pck.gadatatype\",thread-id=\"1\",has_more=\"0\"" \
>>>>>>      "Create ggg1 varobj"
>>>>>>  
>>>>>>  mi_gdb_test "-var-list-children 1 ggg1" \
>>>>>> -    "\\^done,numchild=\"1\",children=\\\[child={name=\"ggg1.i\",exp=\"i\",numchild=\"0\",value=\"42\",type=\"integer\"}\\\],has_more=\"0\"" \
>>>>>> +    "\\^done,numchild=\"1\",children=\\\[child={name=\"ggg1.i\",exp=\"i\",numchild=\"0\",value=\"42\",type=\"integer\",thread-id=\"1\"}\\\],has_more=\"0\"" \
>>>>>>      "list ggg1's children"
>>>>>> diff --git a/gdb/testsuite/gdb.ada/mi_var_array.exp b/gdb/testsuite/gdb.ada/mi_var_array.exp
>>>>>> index c648e7e..c02d4c9 100644
>>>>>> --- a/gdb/testsuite/gdb.ada/mi_var_array.exp
>>>>>> +++ b/gdb/testsuite/gdb.ada/mi_var_array.exp
>>>>>> @@ -48,5 +48,5 @@ mi_gdb_test "-var-create vta * vta" \
>>>>>>      "Create bt varobj"
>>>>>>  
>>>>>>  mi_gdb_test "-var-list-children vta" \
>>>>>> -    "\\^done,numchild=\"2\",children=\\\[child={name=\"vta.n\",exp=\"n\",numchild=\"0\",type=\"bar\\.int\"},child={name=\"vta.f\",exp=\"f\",numchild=\"0\",type=\"array \\(1 .. n\\) of character\"}\\\],.*" \
>>>>>> +    "\\^done,numchild=\"2\",children=\\\[child={name=\"vta.n\",exp=\"n\",numchild=\"0\",type=\"bar\\.int\",thread-id=\"1\"},child={name=\"vta.f\",exp=\"f\",numchild=\"0\",type=\"array \\(1 .. n\\) of character\",thread-id=\"1\"}\\\],.*" \
>>>>>>      "list vta's children"
>>>>>> diff --git a/gdb/testsuite/gdb.mi/mi-break.exp b/gdb/testsuite/gdb.mi/mi-break.exp
>>>>>> index 85f328d..bdd43e0 100644
>>>>>> --- a/gdb/testsuite/gdb.mi/mi-break.exp
>>>>>> +++ b/gdb/testsuite/gdb.mi/mi-break.exp
>>>>>> @@ -213,7 +213,7 @@ proc test_error {} {
>>>>>>      # containing function call, the internal breakpoint created to handle
>>>>>>      # function call would be reported, messing up MI output.
>>>>>>      mi_gdb_test "-var-create V * return_1()" \
>>>>>> -        "\\^done,name=\"V\",numchild=\"0\",value=\"1\",type=\"int\",has_more=\"0\"" \
>>>>>> +        "\\^done,name=\"V\",numchild=\"0\",value=\"1\",type=\"int\",thread-id=\"1\",has_more=\"0\"" \
>>>>>>          "create varobj for function call"
>>>>>>  
>>>>>>      mi_gdb_test "-var-update *" \
>>>>>> diff --git a/gdb/testsuite/gdb.mi/mi-frame-regs.exp b/gdb/testsuite/gdb.mi/mi-frame-regs.exp
>>>>>> new file mode 100644
>>>>>> index 0000000..45f81d6
>>>>>> --- /dev/null
>>>>>> +++ b/gdb/testsuite/gdb.mi/mi-frame-regs.exp
>>>>>> @@ -0,0 +1,183 @@
>>>>>> +# Copyright 1999-2016 Free Software Foundation, Inc.
>>>>>> +
>>>>>> +# This program is free software; you can redistribute it and/or modify
>>>>>> +# it under the terms of the GNU General Public License as published by
>>>>>> +# the Free Software Foundation; either version 3 of the License, or
>>>>>> +# (at your option) any later version.
>>>>>> +#
>>>>>> +# This program is distributed in the hope that it will be useful,
>>>>>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>>>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>>>> +# GNU General Public License for more details.
>>>>>> +#
>>>>>> +# You should have received a copy of the GNU General Public License
>>>>>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>>>>> +
>>>>>> +# Test essential Machine interface (MI) operations
>>>>>> +#
>>>>>> +# Verify that -var-update will provide the correct values for floating
>>>>>> +# and fixed varobjs that represent the pc register.
>>>>>> +#
>>>>>> +
>>>>>> +load_lib mi-support.exp
>>>>>> +set MIFLAGS "-i=mi"
>>>>>> +
>>>>>> +standard_testfile basics.c
>>>>>> +
>>>>>> +if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
>>>>>> +		 executable {debug}] != "" } then {
>>>>>> +     untested mi-frame-regs.exp
>>>>>> +     return -1
>>>>>> +}
>>>>>> +
>>>>>> +# Return the address of the specified breakpoint.
>>>>>> +
>>>>>> +proc breakpoint_address {bpnum} {
>>>>>> +    global hex
>>>>>> +    global expect_out
>>>>>> +    global mi_gdb_prompt
>>>>>> +
>>>>>> +    send_gdb "info breakpoint $bpnum\n"
>>>>>> +    gdb_expect {
>>>>>> +	-re ".*($hex).*$mi_gdb_prompt$" {
>>>>>> +	    return $expect_out(1,string)
>>>>>> +	}
>>>>>> +	-re ".*$mi_gdb_prompt$" {
>>>>>> +	    return ""
>>>>>> +	}
>>>>>> +	timeout {
>>>>>> +	    return ""
>>>>>> +	}
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +# Test that a floating varobj representing $pc will provide the
>>>>>> +# correct value via -var-update as the program stops at
>>>>>> +# breakpoints in different functions.
>>>>>> +
>>>>>> +proc do_floating_varobj_test {} {
>>>>>> +    global srcfile
>>>>>> +    global hex
>>>>>> +    global expect_out
>>>>>> +
>>>>>> +    gdb_exit
>>>>>> +    if {[mi_gdb_start]} then {
>>>>>> +	continue
>>>>>> +    }
>>>>>> +
>>>>>> +    with_test_prefix "floating" {
>>>>>> +	mi_run_to_main
>>>>>> +
>>>>>> +	# Create a floating varobj for $pc.
>>>>>> +	mi_gdb_test "-var-create --thread 1 --frame 0 - @ \$pc" \
>>>>>> +		    "\\^done,.*value=\"$hex.*" \
>>>>>> +	            "create varobj for pc in frame 0"
>>>>>> +
>>>>>> +	set nframes 4
>>>>>> +	for {set i 1} {$i < $nframes} {incr i} {
>>>>>> +
>>>>>> +	    # Run to a breakpoint in each callee function in succession.
>>>>>> +	    # Note that we can't use mi_runto because we need the
>>>>>> +	    # breakpoint to be persistent, so we can use its address.
>>>>>> +	    set bpnum [expr $i + 1]
>>>>>> +	    mi_create_breakpoint \
>>>>>> +	        "basics.c:callee$i" \
>>>>>> +		"insert breakpoint at basics.c:callee$i" \
>>>>>> +		-number $bpnum -func callee$i -file ".*basics.c"
>>>>>> +
>>>>>> +	    mi_execute_to "exec-continue" "breakpoint-hit" \
>>>>>> +			  "callee$i" ".*" ".*${srcfile}" ".*" \
>>>>>> +			  { "" "disp=\"keep\"" } "breakpoint hit"
>>>>>> +
>>>>>> +	    # Get the value of $pc from the floating varobj.
>>>>>> +	    mi_gdb_test "-var-update 1 var1" \
>>>>>> +			"\\^done,.*value=\"($hex) .*" \
>>>>>> +			"-var-update for frame $i"
>>>>>> +	    set pcval $expect_out(3,string)
>>>>>> +
>>>>>> +	    # Get the address of the current breakpoint.
>>>>>> +	    set bpaddr [breakpoint_address $bpnum]
>>>>>> +	    if {$bpaddr == ""} then {
>>>>>> +		unresolved "get address of breakpoint $bpnum"
>>>>>> +		return
>>>>>> +	    }
>>>>>> +
>>>>>> +	    # Check that the addresses are the same.
>>>>>> +	    if {[expr $bpaddr != $pcval]} then {
>>>>>> +	        fail "\$pc does not equal address of breakpoint"
>>>>>> +	    } else {
>>>>>> +	        pass "\$pc equals address of breakpoint"
>>>>>> +	    }
>>>>>> +	}
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +# Create a varobj for the pc register in each of the frames other
>>>>>> +# than frame 0.
>>>>>> +
>>>>>> +proc var_create_regs {nframes} {
>>>>>> +    global hex
>>>>>> +
>>>>>> +    for {set i 1} {$i < $nframes} {incr i} {
>>>>>> +	mi_gdb_test "-var-create --thread 1 --frame $i - \* \$pc" \
>>>>>> +		    "\\^done,.*value=\"$hex.*" \
>>>>>> +	            "create varobj for pc in frame $i"
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +# Check that -var-update reports that the value of the pc register
>>>>>> +# for each of the frames 1 and above is reported as unchanged.
>>>>>> +
>>>>>> +proc var_update_regs {nframes} {
>>>>>> +
>>>>>> +    for {set i 1} {$i < $nframes} {incr i} {
>>>>>> +	mi_gdb_test "-var-update 1 var$i" \
>>>>>> +	            "\\^done,(changelist=\\\[\\\])" \
>>>>>> +	            "pc unchanged in -var-update for frame $i"
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +# Test that fixed varobjs representing $pc in different stack frames
>>>>>> +# will provide the correct value via -var-update after the program
>>>>>> +# counter changes (without substantially changing the stack).
>>>>>> +
>>>>>> +proc do_fixed_varobj_test {} {
>>>>>> +    global srcfile
>>>>>> +
>>>>>> +    gdb_exit
>>>>>> +    if {[mi_gdb_start]} then {
>>>>>> +	continue
>>>>>> +    }
>>>>>> +
>>>>>> +    with_test_prefix "fixed" {
>>>>>> +	mi_run_to_main
>>>>>> +
>>>>>> +	# Run to the function 'callee3' so we have several frames.
>>>>>> +	mi_create_breakpoint "basics.c:callee3" \
>>>>>> +			     "insert breakpoint at basics.c:callee3" \
>>>>>> +			     -number 2 -func callee3 -file ".*basics.c"
>>>>>> +
>>>>>> +	mi_execute_to "exec-continue" "breakpoint-hit" \
>>>>>> +	              "callee3" ".*" ".*${srcfile}" ".*" \
>>>>>> +		      { "" "disp=\"keep\"" } "breakpoint hit"
>>>>>> +
>>>>>> +	# At the breakpoint in callee3 there are 4 frames.  Create a
>>>>>> +	# varobj for the pc in each of frames 1 and above.
>>>>>> +	set nframes 4
>>>>>> +	var_create_regs $nframes
>>>>>> +
>>>>>> +	# Step one instruction to change the program counter.
>>>>>> +	mi_execute_to "exec-next-instruction" "end-stepping-range" \
>>>>>> +		      "callee3" ".*" ".*${srcfile}" ".*" "" \
>>>>>> +		      "next instruction in callee3"
>>>>>> +
>>>>>> +	# Check that -var-update reports that the values are unchanged.
>>>>>> +	var_update_regs $nframes
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>> +do_fixed_varobj_test
>>>>>> +do_floating_varobj_test
>>>>>> +
>>>>>> +mi_gdb_exit
>>>>>> +return 0
>>>>>> diff --git a/gdb/testsuite/gdb.mi/mi-var-cmd.exp b/gdb/testsuite/gdb.mi/mi-var-cmd.exp
>>>>>> index 558cd6c..68e3cf8 100644
>>>>>> --- a/gdb/testsuite/gdb.mi/mi-var-cmd.exp
>>>>>> +++ b/gdb/testsuite/gdb.mi/mi-var-cmd.exp
>>>>>> @@ -381,7 +381,7 @@ mi_gdb_test "-var-update *" \
>>>>>>  	"assign same value to func (update)"
>>>>>>  
>>>>>>  mi_gdb_test "-var-create array_ptr * array_ptr" \
>>>>>> -	"\\^done,name=\"array_ptr\",numchild=\"1\",value=\"$hex <array>\",type=\"int \\*\",has_more=\"0\"" \
>>>>>> +	"\\^done,name=\"array_ptr\",numchild=\"1\",value=\"$hex <array>\",type=\"int \\*\",thread-id=\"1\",has_more=\"0\"" \
>>>>>>  	"create global variable array_ptr"
>>>>>>  
>>>>>>  mi_gdb_test "-var-assign array_ptr array2" \
>>>>>> @@ -608,7 +608,7 @@ mi_check_varobj_value F 7 "check F inside callee"
>>>>>>  # A varobj we fail to read during -var-update should be considered
>>>>>>  # out of scope.
>>>>>>  mi_gdb_test "-var-create null_ptr * **0" \
>>>>>> -    {\^done,name="null_ptr",numchild="0",value=".*",type="int",has_more="0"} \
>>>>>> +    {\^done,name="null_ptr",numchild="0",value=".*",type="int",thread-id="1"has_more="0"} \
>>>>>>      "create null_ptr"
>>>>>>  
>>>>>>  # Allow this to succeed, if address zero is readable, although it
>>>>>> diff --git a/gdb/testsuite/gdb.mi/mi-var-create-rtti.exp b/gdb/testsuite/gdb.mi/mi-var-create-rtti.exp
>>>>>> index 3bcb36c..a8cc76f 100644
>>>>>> --- a/gdb/testsuite/gdb.mi/mi-var-create-rtti.exp
>>>>>> +++ b/gdb/testsuite/gdb.mi/mi-var-create-rtti.exp
>>>>>> @@ -49,6 +49,6 @@ mi_gdb_test "-gdb-set print object on" ".*"
>>>>>>  # We use a explicit cast to (void *) as that is the
>>>>>>  # type that caused the bug this testcase is testing for.
>>>>>>  mi_gdb_test "-var-create sp1 * ((void*)\$sp)" \
>>>>>> -	    "\\^done,name=\"sp1\",numchild=\"0\",value=\"$hex\",type=\"void \\*\",has_more=\"0\"" \
>>>>>> +	    "\\^done,name=\"sp1\",numchild=\"0\",value=\"$hex\",type=\"void \\*\",thread-id=\"1\",has_more=\"0\"" \
>>>>>>  	    "-var-create sp1 * \$sp"
>>>>>>  gdb_exit
>>>>>> diff --git a/gdb/varobj.c b/gdb/varobj.c
>>>>>> index 6f56cba..1e3f192 100644
>>>>>> --- a/gdb/varobj.c
>>>>>> +++ b/gdb/varobj.c
>>>>>> @@ -323,7 +323,7 @@ varobj_create (char *objname,
>>>>>>  	}
>>>>>>  
>>>>>>        p = expression;
>>>>>> -      innermost_block = NULL;
>>>>>> +      innermost_block = block_global_block (block);
>>>>>>        /* Wrap the call to parse expression, so we can 
>>>>>>           return a sensible error.  */
>>>>>>        TRY
>>>>>> @@ -2103,6 +2103,8 @@ new_root_variable (void)
>>>>>>    var->root->floating = 0;
>>>>>>    var->root->rootvar = NULL;
>>>>>>    var->root->is_valid = 1;
>>>>>> +  var->root->thread_id = 0;
>>>>>> +  var->root->next = NULL;
>>>>>>  
>>>>>>    return var;
>>>>>>  }
>>>>>> @@ -2268,7 +2270,9 @@ value_of_root_1 (struct varobj **var_handle)
>>>>>>    back_to = make_cleanup_restore_current_thread ();
>>>>>>  
>>>>>>    /* Determine whether the variable is still around.  */
>>>>>> -  if (var->root->valid_block == NULL || var->root->floating)
>>>>>> +  if (var->root->valid_block == NULL
>>>>>> +      || BLOCK_SUPERBLOCK (var->root->valid_block) == NULL
>>>>>> +      || var->root->floating)
>>>>>>      within_scope = 1;
>>>>>>    else if (var->root->thread_id == 0)
>>>>>>      {
>>>>>>
>>>>>
>>>>
>>>
>> I've created PR mi/20395 for this issue and marked it with the Target
>> Milestone 7.12.  Since it's an issue of returning incorrect data I'm
>> proposing that it's a blocker.
>> thanks
>> --Don
>>
>