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

[Don Breazeal <donb at codesourcery dot com>]

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)
>>>      {
>>>
>>
>