Hi,

With the new build system, TF-M downloads all dependant repositories to the BUILD folder as part of CMAKE configuration. CMake does provide `make clean` target to clean the build and rebuild but this doesn’t track any config changes between the builds. Previously, the CMake workflow was to delete all contents in the BUILD folder before re-configuring for a new build but now this means the developer has to re-download all the dependant git repositories before the project can be build again. This can be a slow and cumbersome process for developers. Deleting the CMakecache.txt doesn’t seem to solve the problem either.

The most obvious solution is to move the cloned repositories outside the BUILD/ folder , so we can follow the previous workflow of deleting the BUILD folder before re-build. The sample test sequence to reproduce the problem is given below:

/* Build secure regressions test suite */

$ make clean; cmake .. -DTFM_PLATFORM=mps2/an521 -DCMAKE_TOOLCHAIN_FILE=../toolchain_GNUARM.cmake  -DTEST_S=ON   -DCMAKE_BUILD_TYPE=Debug; make install

/* reconfigure  and build PSA Crypto API test suite */

$ make clean; cmake .. -DTFM_PLATFORM=mps2/an521 -DCMAKE_TOOLCHAIN_FILE=../toolchain_GNUARM.cmake  -DCMAKE_BUILD_TYPE=Debug -DTEST_PSA_API=CRYPTO; make install

Built binary is still for regression test suite.

There are multiple suggestions to solve the problem, One is to move the clone repositories outside the BUILD/ folder, or introduce a build target like `make cleanall` which does the equivalent  of rm -rf !(lib) within the BUILD folder (i.e the build target will remove all folders except the lib folder which has the cloned repositories). Please let us know of your suggestions on this.

Best Regards

Soby Mathew