[PATCH 1/2] cmake: optionally build `scalar`, too

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Jun 2, 2022, 09:05 UTC
Message-ID: <c155cadfa309e856f13ea7d005870dab706a74ce.1654160735.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1129.git.1654160735.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

Unlike the `Makefile`-based build, the CMake configuration unfortunately does not let us easily encapsulate Scalar's build definition in the `contrib/scalar/` subdirectory: The `scalar` executable needs to link in `libgit.a` and `common-main.o`, for example.

Also, `scalar.c` includes Git's header files, which means that `scalar.c` needs to be compiled with the very same flags as `libgit.a` lest `scalar.o` and `libgit.a` have different ideas of, say, `platform_SHA_CTX`, which would naturally lead to memory corruption, crashes and quite tricky debugging (talking from experience).

To alleviate that lack of encapsulation somewhat, we guard the Scalar parts in `CMakeLists.txt` via the `INCLUDE_SCALAR` environment variable. This not only allows the CMake-based build to exclude Scalar by default, but also gives better visual cues as to which sections are related to Scalar.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 contrib/buildsystems/CMakeLists.txt | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 185f56f414f..c8a802463ba 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -753,6 +753,13 @@ if(CURL_FOUND)
 	endif()
 endif()
 
+if(DEFINED ENV{INCLUDE_SCALAR} AND NOT ENV{INCLUDE_SCALAR} STREQUAL "")
+	add_executable(scalar ${CMAKE_SOURCE_DIR}/contrib/scalar/scalar.c)
+	target_link_libraries(scalar common-main)
+	set_target_properties(scalar PROPERTIES RUNTIME_OUTPUT_DIRECTORY_DEBUG ${CMAKE_BINARY_DIR}/contrib/scalar)
+	set_target_properties(scalar PROPERTIES RUNTIME_OUTPUT_DIRECTORY_RELEASE ${CMAKE_BINARY_DIR}/contrib/scalar)
+endif()
+
 parse_makefile_for_executables(git_builtin_extra "BUILT_INS")
 
 option(SKIP_DASHED_BUILT_INS "Skip hardlinking the dashed versions of the built-ins")
@@ -980,6 +987,13 @@ string(REPLACE "@@BUILD_DIR@@" "${CMAKE_BINARY_DIR}" content "${content}")
 string(REPLACE "@@PROG@@" "git-cvsserver" content "${content}")
 file(WRITE ${CMAKE_BINARY_DIR}/bin-wrappers/git-cvsserver ${content})
 
+if(DEFINED ENV{INCLUDE_SCALAR} AND NOT ENV{INCLUDE_SCALAR} STREQUAL "")
+	file(STRINGS ${CMAKE_SOURCE_DIR}/wrap-for-bin.sh content NEWLINE_CONSUME)
+	string(REPLACE "@@BUILD_DIR@@" "${CMAKE_BINARY_DIR}" content "${content}")
+	string(REPLACE "@@PROG@@" "contrib/scalar/scalar${EXE_EXTENSION}" content "${content}")
+	file(WRITE ${CMAKE_BINARY_DIR}/bin-wrappers/scalar ${content})
+endif()
+
 #options for configuring test options
 option(PERL_TESTS "Perform tests that use perl" ON)
 option(PYTHON_TESTS "Perform tests that use python" ON)

-- 
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