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


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)
>>      {
>>
> 


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