Why does externalproject downloads and compiles every time ?

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7

If you’re using the URL method and don’t specify a hash, I believe the default behavior is that it’s redownloaded every time. I typically use the external project option

UPDATE_DISCONNECTED true

Or for all ExternalProject in that directory scope

set_property(DIRECTORY PROPERTY EP_UPDATE_DISCONNECTED true)

That should stop the constant redownloading on every configure.

I also like external project option

CONFIGURE_HANDLED_BY_BUILD true

That in general will save significant time of reconfiguring external projects besides just the redownloading.