-var-update using formatted value

["Marc Khouzam" <marc dot khouzam at ericsson dot com>]

Hello,

I've been using varObject for a three or four months now and I noticed something weird with -var-update.
-var-update is supposed to show variables that have changed since the last -var-udpate, correct?
It does not seem to work in this case:

int main() {
    int a = 11;   // line 3
    a = 3;         // line 4
}

MI commands:
-break-insert main
-exec-run
-exec-next
-var-create - * a
-var-set-format var1 bin
-var-evaluate-expression var1
-exec-next
-var-update var1
-var-evaluate-expression var1

Session (output simplified with [...])
-break-insert main
^done,...
(gdb) 
-exec-run
^running
(gdb) 
*stopped,reason="breakpoint-hit",[...],line="3"}
(gdb) 
-exec-next
^running
(gdb) 
*stopped,reason="end-stepping-range",[...]",line="4"}
(gdb) 
-var-create - * a
^done,name="var1",numchild="0",value="11",type="int"
(gdb) 
-var-set-format var1 bin
^done,format="binary"
(gdb) 
-var-evaluate-expression var1
^done,value="1011"
(gdb) 
-exec-next
^running
(gdb) 
*stopped,reason="end-stepping-range",[...],line="5"}
(gdb) 
-var-update var1
^done,changelist=[]
(gdb) 
-var-evaluate-expression var1
^done,value="11"

As you might guess, the reason for this is that the binary value of var1 (11 in binary) when doing -var-udpate is the same as the natural value of var1 (11 in decimal)
of the previous -var-udpate (var-create in this case.)  

I believe this behaviour was introduced in version 1.75 of varobj.c in install_new_value(), where instead of comparing value contents, it now compares printed values.
I'm sure there was a good reason to compare printed values, but was this side-effect known?

Another issue with comparing printed values in -var-update is that if a front-end wants to know if a variable object memory -really- changed, it should perform
the -var-udpate using the same format every time, or else var-update will show a change although it is just the format that changed.
But maybe that is what was meant for -var-update to do?

Thanks for your input.

Marc



 
Marc Khouzam
Software Designer, Methods and Tools
 
Ericsson Canada Inc
EMC/Q
8500 Decarie Blvd.
H4P 2N2, Mont-Royal, Qc, Canada
www.ericsson.comOffice: +514 345 7900 x42350
Fax: +514 345 6159
Mobile: +514 951 7191
Email: Marc.Khouzam@ericsson.com




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