CODEWITHSUNDEEP
cmake
Gillespie
Gillespie

Reputation: 6561

Rebuild ExternalProject if source changes

I have an external project:

ExternalProject_Add(
    lighttpd
    URL "${PROJECT_SOURCE_DIR}/ext/lighttpd/lighttpd.tar.gz"
    SOURCE_DIR "${EXTERNAL_INSTALL_PATH}/lighttpd"
)

ExternalProject_Add_Step(
    lighttpd copy2build
    COMMAND cp -a ${EXTERNAL_INSTALL_PATH}/lighttpd/bin/. ${EXECUTABLE_OUTPUT_PATH}
    COMMAND cp -a ${EXTERNAL_INSTALL_PATH}/lighttpd/lib/. ${LIBRARY_OUTPUT_PATH}
    DEPENDEES install
)

The problem is that CMake is not rebuilding lighttpd if lighttpd.tar.gz changes. How can I tell CMake to rebuild this external project if lighttpd.tar.gz changes?

Upvotes: 4

Views: 800

Answers (1)

Samaursa
Samaursa

Reputation: 17197

This is an interesting problem that I don't think ExternalProject_Add solves by it's own.

Note that ExternalProject_Add_Step has an option ALWAYS that you can set to 1 or 0. We'll use that in the following workaround/solution.

You can compute the hash of the file using the following:

file(<MD5|SHA1|SHA224|SHA256|SHA384|SHA512> filename file_hash)

You can then save this variable as an internal cache variable

set(TAR_BALL_HASH ${file_hash} CACHE INTERNAL "")

You can then compare the two variables and if they are the same, set the ALWAYS option of your ExternalProject_Add_Step to 1, otherwise, set it to 0.

Upvotes: 1

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