Multiply defined variables when using gcc v10.2.0

[abergerSRS]

gcc fails to compile test code, throwing "multiple definition of" errors when using gcc v10.2.0. Issue is not present with gcc v8.1.0

[mundodisco8]

Same here. I attach a test project

Globals.zip

This is the output with GCC 5

And this is the output with GCC 10

[CezaryGapinski]

Please check this link about porting to GCC 10. Now -fno-common flag is used by default what cause problems.

I think you can add this section to your project.yml file to achieve behavior like for previous GCC version:

:flags:
  :test:
    :compile:
      :*:
        - -fcommon

[groundstack]

Would it be a more 'proper' solution to change the code with extern variables or modify the project.yml with "f-common" flag? Thanks!

[johnwcowan]

The C standards require that variables be defined only once, e.g. int x;, and be declared with extern int x; in all other files. In particular, a header file should almost always have extern declarations. -fcommon is basically a workaround for old programs that don't conform.