[libclang][Cygwin] Provide unversioned DLL file alongside versioned one #147132
Conversation
On Cygwin, a shared library target generates a versioned DLL file like
"cyg${OUTPUT_NAME}-${VERSION}.dll" and an import library
"lib${OUTPUT_NAME}.dll.a", but it does *not* generate the expected
unversioned symlink "cyg${OUTPUT_NAME}.dll" as is typical on other Unix-like platforms.
However, `dlopen()` calls typically use the unversioned form (e.g. "cygclang.dll"),
and this is consistent with usage on other platforms. In particular, `clang-python`
relies on this behavior. Although the Cygwin runtime can resolve other forms like
"libclang.so" or "libclang.dll", a symlink alone won't suffice here, as `dlopen()`
ultimately calls `LoadLibraryExW`, which does not follow Cygwin-style symlinks.
Therefore, this patch installs an unversioned copy of the DLL without the version
suffix to improve compatibility with `dlopen()` and tools like `clang-python`.
llvmbot
added
clang
|
@llvm/pr-subscribers-clang Author: Tomohiro Kashiwada (kikairoya) ChangesOn Cygwin, a shared library target generates a versioned DLL file like However, Therefore, this patch installs an unversioned copy of the DLL without the version suffix to improve compatibility with Full diff: https://github.com/llvm/llvm-project/pull/147132.diff 1 Files Affected:
diff --git a/clang/tools/libclang/CMakeLists.txt b/clang/tools/libclang/CMakeLists.txt
index ac7a9a8db37c0..9c5ca26aab099 100644
--- a/clang/tools/libclang/CMakeLists.txt
+++ b/clang/tools/libclang/CMakeLists.txt
@@ -157,15 +157,28 @@ if(ENABLE_STATIC)
endif()
if(ENABLE_SHARED)
- if(WIN32)
+ if(WIN32 OR CYGWIN)
set_target_properties(libclang
PROPERTIES
VERSION ${LIBCLANG_LIBRARY_VERSION}
DEFINE_SYMBOL _CINDEX_LIB_)
- # Avoid declaring clang c++ symbols that are statically linked into libclang as dllimport'ed.
- # If llvm/libclang-cpp dll is also being built for windows clang c++ symbols will still be
- # implicitly be exported from libclang.
- target_compile_definitions(libclang PRIVATE CLANG_BUILD_STATIC)
+ if (CYGWIN)
+ # On Cygwin environment, a library target generates "cyg${OUTPUT_NAME}-${VERSION}.dll" and "lib${OUTPUT_NAME}.dll.a" but
+ # don't provide link "cyg${OUTPUT_NAME}.dll" differs from expected as other Unix platforms.
+ # Although, to dlopen(), usually "cyg${OUTPUT_NAME}.dll" will be passed (or "lib${OUTPUT_NAME}.dll" and "lib${OUTPUT_NAME}.so"
+ # are also viable as Cygwin runtime replaces those prefix and suffix), which is same manner to other Unix platforms,
+ # and clang-python does so.
+ # Thus, put a copy of dll named without version suffix to convinience to use of dlopen(). A symbolic link can't be
+ # viable here as the path passed to dlopen() will be passed directly to LoadLibraryExW, so it must be a real file.
+ set(UNPAINTED_TARGET_NAME "$<TARGET_FILE_DIR:libclang>/$<TARGET_FILE_PREFIX:libclang>clang$<TARGET_FILE_SUFFIX:libclang>")
+ add_custom_command(TARGET libclang POST_BUILD
+ COMMAND ${CMAKE_COMMAND} -E copy "$<TARGET_FILE:libclang>" "${UNPAINTED_TARGET_NAME}")
+ install(FILES "${UNPAINTED_TARGET_NAME}" DESTINATION "${CMAKE_INSTALL_BINDIR}" COMPONENT libclang)
+ endif()
+ # Avoid declaring clang c++ symbols that are statically linked into libclang as dllimport'ed.
+ # If llvm/libclang-cpp dll is also being built for windows clang c++ symbols will still be
+ # implicitly be exported from libclang.
+ target_compile_definitions(libclang PRIVATE CLANG_BUILD_STATIC)
elseif(APPLE)
set(LIBCLANG_LINK_FLAGS " -Wl,-compatibility_version -Wl,1")
set(LIBCLANG_LINK_FLAGS "${LIBCLANG_LINK_FLAGS} -Wl,-current_version -Wl,${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
|
If dlopen doesn't work on a Cygwin symlink, that is a bug in dlopen and should be fixed in Cygwin. |
I had been misunderstood the functionality. That's cool. Thank you. I made changes for description, commit and function body to use symlink. |
|
|
|
Updated for use relative path to link target. |
|
Perhaps the change in https://github.com/llvm/llvm-project/pull/136599/files#diff-f60dae8e82f67fa5e534e9ea566430d5b79f36119020865dc37b95d9a3635c5eR753 should be reconsidered instead, I wasn't thinking about dlopen in that case. |
|
I'm thinking about each DLLs:
I had focused to make a symlink So, installed-tree will be:
I would like to know if there are any concerns to do this. |
|
@mstorsjo ? I imagine whatever scheme is adopted should be considered with consistency with MinGW also. |
On Cygwin, a shared library target generates a versioned DLL file like
cyg${OUTPUT_NAME}-${VERSION}.dlland an import librarylib${OUTPUT_NAME}.dll.a, but it does not generate the expected unversioned symlinkcyg${OUTPUT_NAME}.dllas is typical on other Unix-like platforms.However,
dlopen()calls typically use the unversioned form (e.g.cygclang.dll), and this is consistent with usage on other platforms. In particular,clang-pythonrelies on this behavior.This patch creates a symbolic link named "cygclang.dll" pointing to the versioned DLL to improve compatibility with existing tooling and usage patterns.