TL;DR
I was curious - I have the same behavior with 32 bit boards, it does not display the info and unfortunately this seems to come possibly from the toolset and the way the platform.txt and boards.txt file are built
Recipes to compute binary sketch size
At the end of the build the Arduino IDE shows the final binary sketch size to the user. The size is calculated using the recipe recipe.size.pattern. The output of the command executed using the recipe is parsed through the regular expression set in the property recipe.size.regex. The regular expression must match the sketch size.
IF YOU WANT TO EXPLORE
you can get the info from command line (at least on a Mac that's how I would do it)
For example I opened Blink.ino from the examples, I set the IDE preferences to be verbose for compile so that I can see where is the temp directory for my sketch
Look for something like this in the compiler output log (many similar lines)
[color=green]/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/[/color]avr-gcc-ar" rcs "[color=blue]/var/folders/xk/mwl4yt3j5rsgdmgmgjlqsk7w0000gn/T/buildd5ae82e677127ac286f51de66781d807.tmp[/color]/core/core.a" "/var/fol....
the green part is where then compilers tools for the platform are
the blue part is your temporary folder for your project --> copy that path
open a Terminal.app and go to the temp folder where your sketch is being built
cd /var/folders/xk/mwl4yt3j5rsgdmgmgjlqsk7w0000gn/T/buildd5ae82e677127ac286f51de66781d807.tmp
there you should see (do a ls) a Blink.ino.elf file
and you can launch the command
[color=green]/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/[/color][b][color=navy]avr-size[/color][/b] -C [color=red]--mcu=atmega328p[/color] Blink.ino.elf
and you get
AVR Memory Usage ---------------- Device: atmega328p Program: 928 bytes (2.8% Full) (.text + .data + .bootloader) Data: 9 bytes (0.4% Full) (.data + .bss + .noinit)
in red this is describing your architecture. You can get the list of known architectures with
/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/avr-size --mlist
so this is what the IDE is showing to you
Now if you use a non AVR architecture (ARM for the DUE, Intel for the 101) then the tools are in a different place (when you downloaded the boards) - on my Mac they are in my home directory at
~/Library/Arduino15/packages/arduino/tools/arm-none-eabi-gcc/4.8.3-2014q1/bin/[color=blue]arm-none-eabi-size[/color]
~/Library/Arduino15/packages/Intel/tools/arc-elf32/1.6.9+1.0.1/bin/[color=blue]arc-elf32-size[/color]
the challenge is you run those with the --h option to get the help, is that they have no option to give you all the details, so this could ve why the IDE does not give you the info.
So where do they define the compilation option?
the info is collected in the platform.txt where they define
compiler.size.cmd=arc-elf32-size ... ## Compute size recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf" recipe.size.regex=^(?:text|ctors|rodata|datas)\s+([0-9]+).*
whereas for your standard avr platform
compiler.size.cmd=avr-size ... ## Compute size recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf" recipe.size.regex=^(?:\.text|\.data|\.bootloader)\s+([0-9]+).* recipe.size.regex.data=^(?:\.data|\.bss|\.noinit)\s+([0-9]+).* recipe.size.regex.eeprom=^(?:\.eeprom)\s+([0-9]+).*
But wait — they don't do a -C with the platform info, they do a -A and then a regex to extract the info. They clearly have more regex for the AVR platform than for the other architecture...
the size expression for the 101 gives
> ~/Library/Arduino15/packages/Intel/tools/arc-elf32/1.6.9+1.0.1/bin/arc-elf32-size -A Blink.ino.elf Blink.ino.elf : section size addr text 13620 1073954816 ctors 12 1073968436 rodata 436 1073968448 datas 3196 2818629632 bss 1916 2818632828 heap 8192 2818634744 stack 2560 2818642936 .comment 149 0 Total 30081
and for the UNO
/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/avr-size -A Blink.ino.elf Blink.ino.elf : section size addr .data 0 8388864 .text 928 0 .bss 9 8388864 .comment 17 0 .note.gnu.avr.deviceinfo 64 0 .debug_info 1524 0 .debug_abbrev 1442 0 .debug_line 26 0 .debug_str 520 0 Total 4530
couldn't they get from the knowledge of the board and this info what you need... probably could...
I guess someone with more info can dig from here or comment but hope this helps you get further info on true memory usage through command line.