Please follow the guide in yellow above

Today I got a similar set of duplicate libraries error message under the Arduino IDE that compiled clean yesterday.

The log (attached) also shows multiple library messages for SPI and WiFi101 and Adafruit_ZeroDMA duplicates but compiles clean if I change the board to Arduino Uno.  It compiled clean for the Feather yesterday several times.  I am not making any library changes myself.

My apologies for missing that!  Will send in email as no option to attach file seen.

This is some sort of permissions issue. A standard part of all arduino builds is too append all compiled core files into an archive file (.a extension)

The error in our output says that gcc is unable to rename the .a file. The error appears when an attempt to add the 2nd core file is made. 

The two lines can be pasted into a cmd prompt. Visual Micro does not have any interaction with the running of the archive command. Both the following lines should run without error but on your pc they are not. 

\7-2017q4/bin/arm-none-eabi-ar" rcs 769ed5\core.a" 769ed5\core\pulse_asm.S.o"
\7-2017q4/bin/arm-none-eabi-ar" rcs 769ed5\core.a" 769ed5\core\cortex_handlers.c.o" 

One solution might be to run vs as administrator, another might be to change the permissions for the VMBCore folder.

You could also switch off "vmicro>compiler>shared cache for cores". Switching off the shared cache will cause visual micro to build into the temp build folder that each project uses. 

Then, if needed, you can override the location of the temp build folder in vmicro>general>options. Pointing to a folder with higher permissions.

Lastly a thught to check your virus checker isn't blocking an disk operations such as file delete in the "C:\Users\nrcep\AppData\Local\Temp\VMBCore" folder.

Thank you!  Will try all that.

The permission changes and run as administrator did not help, but

"You could also switch off "vmicro>compiler>shared cache for cores". Switching off the shared cache will cause visual micro to build into the temp build folder that each project uses."

seems to have fixed it.  Have run 6 compiles with no problem.

Thank you so very much!!

It's the same problem. Not a vmicro issue but a pc issue. The commands that fail are shown previously and can be validated by running the cmd suggested earlier.

As I said the commands are used in all arduino builds and are not a known issue. Therefore it does point to a problem with your pc. I mentioned the virus checker previously, I suggest you exclude the build folder(s) from the virus checker if you think it is causing the issue. something is stopping a file that has just been created from being overritten or deleted so that suggests virus or malware checkers.

arm-none-eabi-ar*: unable to rename feather_m0\Release\core.a; reason: File exists
Error creating archive 

Thanks for emailing and update to this issue. You confirmed that it was a virus checker issue incorrectly causing the file to be locked.