gokturk created this revision. gokturk added reviewers: ilya-biryukov, nridge, kadircet, beanz, compnerd. Herald added subscribers: cfe-commits, usaxena95, s.egerton, lenary, PkmX, jfb, arphaman, jkorous, simoncook, mgorny. Herald added a project: clang.
The CheckAtomic module performs two tests to determine if passing '-latomic' to the linker is required: one for 64-bit atomics, and another for non-64-bit atomics. clangd only uses the result from HAVE_CXX_ATOMICS64_WITHOUT_LIB. This is incomplete because there are uses of non-64-bit atomics in the code, such as the ReplyOnce::Replied of type std::atomic<bool> defined in clangd/ClangdLSPServer.cpp. It is possible to have a requirement for an explicit '-latomic' for non-64-bit atomics and not have for atomics64. One example is the RISC-V rv64 (64-bit) architecture with the 'A' (atomic) extension, where the host compiler gcc will convert any 64-bit atomic operation to their hardware assembly equivalents, giving the impression that '-latomic' is not required, while failing on 8-bit atomic operations as there is no hardware support for that and linking against libatomic is necessary. As a matter of fact, clang-tools-extra (commit 5c40544fa40bfb85ec888b6a03421b3905e4a4e7) fails to compile with: /usr/lib/gcc/riscv64-unknown-linux-gnu/9.1.0/../../../../riscv64-unknown-linux-gnu/bin/ld: tools/extra/clangd/CMakeFiles/obj.clangDaemon.dir/ClangdLSPServer.cpp.o: in function `.L0 ' : ClangdLSPServer.cpp:(.text._ZN5clang6clangd15ClangdLSPServer14MessageHandler9ReplyOnceclEN4llvm8ExpectedINS4_4json5ValueEEE[_ZN5clang6clangd15ClangdLSPServer14MessageHandler9ReplyOnceclEN4llvm8ExpectedINS4_4json5ValueEEE]+0x2a): undefined reference to `__atomic_exchange_1' collect2: error: ld returned 1 exit status Fix by also checking for the result of HAVE_CXX_ATOMICS_WITHOUT_LIB. See also: https://reviews.llvm.org/D68964 Repository: rG LLVM Github Monorepo https://reviews.llvm.org/D69869 Files: clang-tools-extra/clangd/CMakeLists.txt Index: clang-tools-extra/clangd/CMakeLists.txt =================================================================== --- clang-tools-extra/clangd/CMakeLists.txt +++ clang-tools-extra/clangd/CMakeLists.txt @@ -30,7 +30,7 @@ endif() set(CLANGD_ATOMIC_LIB "") -if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB) +if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB OR NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB) list(APPEND CLANGD_ATOMIC_LIB "atomic") endif()
Index: clang-tools-extra/clangd/CMakeLists.txt =================================================================== --- clang-tools-extra/clangd/CMakeLists.txt +++ clang-tools-extra/clangd/CMakeLists.txt @@ -30,7 +30,7 @@ endif() set(CLANGD_ATOMIC_LIB "") -if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB) +if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB OR NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB) list(APPEND CLANGD_ATOMIC_LIB "atomic") endif()
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