c-kernel: avoid unnecessary rebuilds due to __pycache__ directories

Previously, we would rebuild the kernel if any file in the `seL4` repository changed since previous `cmake` setup. Since the kernel build after the `cmake` setup generates `__pycache__` directories in the `seL4` tree, this would cause some unnecessary rebuilds. This commit explicitly excludes `__pycache__` directories from the set of files considered to be dependencies of the kernel build. Signed-off-by: Matthew Brecknell <[email protected]>
seL4 · Apr 17, 2020 · d8364c9 · d8364c9
1 parent 18c9f36
commit d8364c9
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/spec/cspec/c/kernel.mk b/spec/cspec/c/kernel.mk
@@ -66,7 +66,11 @@ ifndef ISABELLE_PROCESS
   export ISABELLE_PROCESS:=${ISABELLE_HOME}/bin/isabelle-process
 endif
 
-KERNEL_DEPS := $(shell find ${SOURCE_ROOT} -type f)
+# __pycache__ directories are the only in-tree products of the kernel build.
+# But since they are generated after the cmake setup, they would cause unnecessary
+# kernel rebuilds if we treated them as dependencies of the kernel build.
+# We avoid this by excluding __pycache__ directories from the kernel dependencies.
+KERNEL_DEPS := $(shell find ${SOURCE_ROOT} -name __pycache__ -prune -o -type f -print)
 
 # Top level rule for rebuilding kernel_all.c_pp
 ${KERNEL_BUILD_ROOT}/kernel_all.c_pp: ${KERNEL_BUILD_ROOT}/.cmake_done