From b46f8c3bf8f05be53502381550f6c8ecfc562a50 Mon Sep 17 00:00:00 2001 From: got3nks Date: Fri, 7 Aug 2026 10:53:15 +0200 Subject: [PATCH] fix(cmake): detect libatomic with a link probe instead of find_library (#454) On 32-bit targets the throttler's std::atomic needs libatomic (the ops expand to __atomic_*_8 library calls). The availability check used find_library(atomic), which only searches standard filesystem paths. With GCC, libatomic ships inside the compiler's own runtime dir (e.g. .../lib/gcc14/), which isn't on that path, so find_library false-fails and configure aborts -- even though `-latomic` links fine because the GCC driver resolves its internal copy (reported on MacPorts, #453). Replace find_library with check_library_exists(atomic __atomic_load_8), which links a probe with `-latomic` through the compiler driver. It succeeds wherever the flag actually links -- GCC's internal libatomic or a system libatomic (Clang / distro packages, versioned or not) -- and only errors when the flag genuinely can't link. The 32-bit "require libatomic" decision and the FATAL_ERROR guidance are unchanged; only the availability probe changes. Closes #453. --- CMakeLists.txt | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/CMakeLists.txt b/CMakeLists.txt index 1a25468b9..6d41978f8 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -297,15 +297,21 @@ endif() # require libatomic unconditionally on 32-bit builds. set (LIBATOMIC "") if (CMAKE_SIZEOF_VOID_P EQUAL 4) - # Accept either the unversioned `libatomic.so` (Debian / Fedora / - # Arch ship it via the -dev / -devel package) or the versioned-only - # `libatomic.so.1` (openSUSE ships only the latter -- there's no - # separate -devel package). Listing the unversioned name first keeps - # the canonical path preferred when both are present. - find_library (LIBATOMIC_LIBRARY NAMES atomic libatomic.so.1) - if (LIBATOMIC_LIBRARY) + # Probe with a compiler-driven LINK test, not find_library. With GCC, + # libatomic ships inside the compiler's own runtime dir (e.g. + # .../lib/gcc14/) which is not on find_library's filesystem search + # path, so find_library false-fails even though `-latomic` links fine + # -- the GCC driver resolves its internal libatomic (MacPorts, #453). + # check_library_exists links a probe with `-latomic` through the + # compiler driver, so it succeeds wherever the flag actually links: + # GCC's internal copy, or a system libatomic (Clang / distro -dev + # packages, versioned or not). This replaces the earlier find_library + # lookup that only searched standard library paths. + include (CheckLibraryExists) + check_library_exists (atomic __atomic_load_8 "" HAVE_LIBATOMIC) + if (HAVE_LIBATOMIC) set (LIBATOMIC atomic) - message (STATUS "32-bit target: linking libatomic for std::atomic (${LIBATOMIC_LIBRARY})") + message (STATUS "32-bit target: linking libatomic for std::atomic") else() message (FATAL_ERROR "32-bit target detected (sizeof(void*) == 4). aMule's " -- 2.55.0