This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
[PING] Re: [PATCH v3] PR mi/20395 - Fix -var-update for registers in frames 1 and up
On 10/14/2016 9:59 AM, Don Breazeal wrote:
> On 10/6/2016 5:05 PM, Andrew Burgess wrote:
>> * Don Breazeal <donb@codesourcery.com> [2016-10-04 13:56:37 -0700]:
>>
>>> +
>>> + # 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"
>>
>> This PASS is repeated multiple times and is not unique, which I think
>> test names are supposed to be.
>>
>> Otherwise it looks fine to me, though I'm not a maintainer, so can't
>> approve the patch :)
>>
>> Thanks,
>> Andrew
>>
>
> Thanks Andrew. I've added a second "with_test_prefix" inside the
> offending loop to address this. The updated patch follows below,
> as well as the comments from the previous email detailing the
> changes prior to this.
> --Don
>
> On 10/4/2016 1:56 PM, Don Breazeal wrote:
>> I have finally gotten back to this patch and would like to revive it.
>>
>> Pedro, you had two concerns about the previous version of this patch.
>> 1) In varobj.c:varobj_create, the patch changed innermost_block before
>> the call to the expression parser. You pointed out that
>> innermost_block is an output parameter.
>>
>> 2) The patch had a side-effect of adding a thread-id field to the
>> output of the -var-update command for global variables. You were
>> concerned that this wasn't consistent with the documentation and
>> could potentially break front-ends.
>>
>> Here is a new version of the patch. It now assigns innermost_block
>> in a special case for registers after expression parsing is complete.
>> Because it does this just for registers, the output of -var-update
>> for globals is unaffected.
>>
>> This does introduce some special case code, which Andrew had wanted
>> to avoid when he reviewed the original patch. However, with the need
>> to distinguish between registers and globals wrt setting the block, I
>> don't see a way around it.
>>
>> Updated patch follows.
>>
>
> 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 set innermost block to the global block when creating
> a register varobj. Then varobj_create sets varobj->root->frame for
> register varobjs, and varobj_update will select the correct frame
> for register varobjs.
>
> We attempted several 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, breaking 'display' for registers.
> * setting innermost_block in varobj_create prior to calling the
> expression parser. This modified an output parameter on input
> and caused side-effects to -var-update output for globals.
>
> Tested on x86_64 Linux native and native-gdbserver, no regressions.
>
> gdb/testsuite/ChangeLog:
> 2016-10-14 Don Breazeal <donb@codesourcery.com>
>
> * gdb.mi/mi-frame-regs.exp: New test.
>
> gdb/ChangeLog:
> 2016-10-14 Don Breazeal <donb@codesourcery.com>
> Andrew Burgess <andrew.burgess@embecosm.com>
>
> PR mi/20395
> * varobj.c (varobj_create): For registers, assign
> innermost_block to the global block.
>
> ---
> gdb/testsuite/gdb.mi/mi-frame-regs.exp | 184
> +++++++++++++++++++++++++++++++++
> gdb/varobj.c | 8 ++
> 2 files changed, 192 insertions(+)
>
> 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..829bc07
> --- /dev/null
> +++ b/gdb/testsuite/gdb.mi/mi-frame-regs.exp
> @@ -0,0 +1,184 @@
> +# 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 floating varobj for pc in frame 0"
> +
> + set nframes 4
> + for {set i 1} {$i < $nframes} {incr i} {
> + with_test_prefix "frame $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/varobj.c b/gdb/varobj.c
> index fb1349a..80738af 100644
> --- a/gdb/varobj.c
> +++ b/gdb/varobj.c
> @@ -348,6 +348,14 @@ varobj_create (char *objname,
> " as an expression.\n");
> return NULL;
> }
> + else if (var->root->exp->elts[0].opcode == OP_REGISTER)
> + {
> + /* Force the scope of a register varobj to be the global
> + block. This allows it to be associated with a frame
> + and a thread. */
> + gdb_assert (innermost_block == NULL);
> + innermost_block = block_global_block (block);
> + }
>
> var->format = variable_default_display (var);
> var->root->valid_block = innermost_block;
>
Ping.
thanks,
--Don