cmake: symlink whole build dir not just .json file

It turned out that symlinking compile_commands.json from the top level
source dir has some issues:
  * file is not created on Windows and symlinking may cause an error
  * some IDEs create their own json and error out b/c a file exists

Since clangd also looks for the json in build/ directories by default,
we now symlink the whole build directory instead, not just the json file.

This approach requires for the existing build/ dir in the repo to
vanish. Luckily it only contains one automake include file, which is
moved to the top level source dir.

Lastly, make this an opt-in feature, so that the default configuration
of the buildsystem never causes a build failure because of this.

Change-Id: Ib1a5c788269949d8de95d1da2cb0c32a65bf13f2
Signed-off-by: Heiko Hund <[email protected]>
Acked-by: Gert Doering <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg28061.html
Signed-off-by: Gert Doering <[email protected]>

.gitignore

@@ -40,7 +40,7 @@ m4/ltsugar.m4
 m4/ltversion.m4
 m4/lt~obsolete.m4
 
-compile_commands.json
+build
 doc/openvpn-examples.5
 doc/openvpn-examples.5.html
 doc/openvpn.8

CMakeLists.txt

@@ -43,9 +43,17 @@ option(USE_WERROR "Treat compiler warnings as errors (-Werror)" ON)
 set(PLUGIN_DIR /usr/local/lib/openvpn/plugins CACHE FILEPATH "Location of the plugin directory")
 
 # Create machine readable compile commands
-set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
-file(CREATE_LINK ${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json
-                 ${CMAKE_CURRENT_SOURCE_DIR}/compile_commands.json SYMBOLIC)
+option(ENABLE_COMPILE_COMMANDS "Generate compile_commands.json and a symlink for clangd to find it" OFF)
+if (ENABLE_COMPILE_COMMANDS)
+    if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/build AND NOT IS_SYMLINK ${CMAKE_CURRENT_SOURCE_DIR}/build)
+        message(FATAL_ERROR "The top level source directory contains a 'build' file or directory. Please remove or rename it. CMake creates a symlink with that name during build.")
+    endif()
+    set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
+    add_custom_target(
+        symlink-build-dir ALL
+        ${CMAKE_COMMAND} -E create_symlink ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/build
+        )
+endif ()
 
 # AddressSanitize - use CXX=clang++ CC=clang cmake -DCMAKE_BUILD_TYPE=asan to build with ASAN
 set(CMAKE_C_FLAGS_ASAN

Makefile.am

@@ -42,6 +42,7 @@ CLEANFILES = \
 EXTRA_DIST = \
 	contrib \
 	debug \
+	ltrc.inc \
 	CMakeLists.txt \
 	CMakePresets.json \
 	config.h.cmake.in
@@ -53,7 +54,7 @@ BUILT_SOURCES = \
 	config-version.h
 endif
 
-SUBDIRS = build distro include src sample doc tests
+SUBDIRS = distro include src sample doc tests
 
 dist_doc_DATA = \
 	README \

README.cmake.md

@@ -135,3 +135,17 @@ to cmake to be able to use these builds.
 The `unix-native` CMake preset is available for these builds. This preset does
 not require VCPKG and instead assumes all build-dependencies are provided by
 the system natively.
+
+Generating compile_commands.json
+--------------------------------
+
+To have the CMake buildsystem generate compile_commands.json you can specify
+`-DENABLE_COMPILE_COMMANDS=ON` on the command line or enable the CMake option
+another way you like. For supported generators the file will then be created.
+Additionally, the buildsystem will create a symlink `build/` to the --preset
+build directory that contains the generated JSON file. This is done so that
+clangd is able to find it.
+
+Enabling this option may cause an error on Windows, since creating a symlink
+is a privileged operation there. If you enable Developer Mode for the system,
+symlinks can be created by regular users.

configure.ac

@@ -1536,7 +1536,6 @@ AC_SUBST([TEST_CFLAGS])
 
 AC_CONFIG_FILES([
 	Makefile
-	build/Makefile
 	distro/Makefile
 	distro/systemd/Makefile
 	doc/Makefile

src/openvpn/Makefile.am

@@ -9,7 +9,7 @@
 #  Copyright (C) 2006-2012 Alon Bar-Lev <[email protected]>
 #
 
-include $(top_srcdir)/build/ltrc.inc
+include $(top_srcdir)/ltrc.inc
 
 MAINTAINERCLEANFILES = \
 	$(srcdir)/Makefile.in

src/openvpnmsica/Makefile.am

@@ -18,7 +18,7 @@
 #  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 
-include $(top_srcdir)/build/ltrc.inc
+include $(top_srcdir)/ltrc.inc
 
 MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
 

src/openvpnserv/Makefile.am

@@ -9,7 +9,7 @@
 #  Copyright (C) 2006-2012 Alon Bar-Lev <[email protected]>
 #
 
-include $(top_srcdir)/build/ltrc.inc
+include $(top_srcdir)/ltrc.inc
 
 MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
 

src/tapctl/Makefile.am

@@ -18,7 +18,7 @@
 #  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 
-include $(top_srcdir)/build/ltrc.inc
+include $(top_srcdir)/ltrc.inc
 
 MAINTAINERCLEANFILES = $(srcdir)/Makefile.in