Files
falco/cmake/modules/DownloadStringViewLite.cmake
Mark Stemm ad90209177 Always skip update command for git based external projects
I noticed that some external projects were being reconfigured/built
with every make, even though no files in the external project had been
updated.

With some debugging I noticed that git based external projects were
re-running their "update" step every time, and that in turn caused the
configure/build/install steps to re-run as well. (Generally the build
step is a no-op as the Makefile/etc. in the external project is well
formed and doesn't do anything, but the configure/install steps still
run).

It seems related to this cmake bug:
https://gitlab.kitware.com/cmake/cmake/-/issues/19703. In short, the
git update step for an external project does not create any "done"
file that denotes that the files are still up-to-date. Without that
"done" file, the update step is always run, and that in turn causes
the other steps for the external project to re-run as well.

The best way to fix this seems to be to skip the update step by
defining an empty UPDATE_COMMAND. As long as the downloaded code for a
given hash/tag/etc does not change, the update step is unnecessary.

And if we *really* wanted to ensure unchanged dependencies, we would
download our own copies anyway.

Making this change significantly cleans up the falco build to avoid
rebuilding git based external dependencies.

Signed-off-by: Mark Stemm <mark.stemm@gmail.com>
2022-02-18 16:47:43 +01:00

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CMake

#
# Copyright (C) 2020 The Falco Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the License.
#
include(ExternalProject)
set(STRING_VIEW_LITE_PREFIX ${CMAKE_BINARY_DIR}/string-view-lite-prefix)
set(STRING_VIEW_LITE_INCLUDE ${STRING_VIEW_LITE_PREFIX}/include)
message(STATUS "Using bundled string-view-lite in ${STRING_VIEW_LITE_INCLUDE}")
ExternalProject_Add(
string-view-lite
PREFIX ${STRING_VIEW_LITE_PREFIX}
GIT_REPOSITORY "https://github.com/martinmoene/string-view-lite.git"
GIT_TAG "v1.4.0"
CONFIGURE_COMMAND ""
BUILD_COMMAND ""
UPDATE_COMMAND ""
INSTALL_COMMAND
${CMAKE_COMMAND} -E copy ${STRING_VIEW_LITE_PREFIX}/src/string-view-lite/include/nonstd/string_view.hpp
${STRING_VIEW_LITE_INCLUDE}/nonstd/string_view.hpp)