CMake: Link xz against Threads::Threads if using pthreads

The liblzma target was recently changed to link against Threads::Threads
with the PRIVATE keyword. I had forgotten that xz itself depends on
pthreads too due to pthread_sigmask(). Thus, the build broke when
building shared liblzma and pthread_sigmask() wasn't in libc.

Thanks to Peter Seiderer for the bug report.

Fixes: ac05f1b0d7cda1e7ae79775a8dfecc54601d7f1c
Fixes: https://github.com/tukaani-project/xz/issues/129#issuecomment-2204522994
(cherry picked from commit b3e53122f42796aaebd767bab920cf7bedf69966)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 70435bac4b5dc5923229f4717cf1407a76e5ae3d..75108c12aca4189f5ac73900be4299c891128a83 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1776,6 +1776,19 @@ if(NOT MSVC OR MSVC_VERSION GREATER_EQUAL 1900)
 
     target_link_libraries(xz PRIVATE liblzma libgnu)
 
+    if(USE_POSIX_THREADS)
+        # src/xz/signals.c uses mythread_sigmask() which with POSIX
+        # threads calls pthread_sigmask(). Thus, we need the threading
+        # library as a dependency for xz. The liblzma target links against
+        # Threads::Threads PRIVATEly, thus that won't provide the pthreads
+        # symbols for xz.
+        #
+        # NOTE: The build may work without this if the symbol is in libc
+        # but it is mandatory to have this here to keep it working with
+        # all pthread implementations.
+        target_link_libraries(xz PRIVATE Threads::Threads)
+    endif()
+
     target_compile_definitions(xz PRIVATE ASSUME_RAM=128)
 
     if(WIN32)