GHC 8.8.2 Bootstrap Build Fails on macOS Catalina 10.15, undeclared identifier 'TAG_MASK'

Ben Gamari ben at
Fri Jan 17 20:58:08 UTC 2020

Steven Smith <steve.t.smith at> writes:

> I’m trying to upgrade the MacPorts ghc install to the latest 8.8.2.
> The build fails with:
>> error: use of undeclared identifier 'TAG_MASK'
>> :info:build         return (StgWord)p & TAG_MASK;
> This is an error observed with previous ghc versions and on other
> systems, so I do not believe it is macOS-specific. Also, the MacPorts
> build process simply follows the ghc Build & Install instructions:
> Is there a simple fix by adding an extra flag somewhere?
Sigh, this is #17146 which should have been backported. I'll have to
investigate how this slipped through the cracks.

Thanks for raising this.


- Ben
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