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

[Don Breazeal <donb at codesourcery dot com>]

Hi, see below,

On 7/20/2016 2:06 PM, Don Breazeal wrote:
> ping
> 
> On 7/11/2016 7:48 AM, Don Breazeal wrote:
>>
>> ping
>>
>> 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