build: statically link OpenSSL into the static library

Pass OPENSSL_STATIC=1 to the staticlib cargo_build() invocation so
openssl-sys links OpenSSL statically into libscylla-cpp-driver_static.a.
This makes the static archive truly self-contained — users only need
to link system libraries and OpenSSL's pkg-config dependencies.

Since the cdylib and staticlib builds share CARGO_TARGET_DIR but pass
different OPENSSL_STATIC values, they must not run concurrently —
openssl-sys declares rerun-if-env-changed for that variable, and
parallel invocations would thrash its build script cache. Serialize
by making the staticlib target depend on the cdylib target when both
are enabled.

Append platform-specific system libraries to the static .pc file's
Libs: line via @native_static_libs@. These are needed by the Rust
runtime (pthreads, libdl, libm, etc.) and must be provided by the
final linker when linking the static archive into an executable.

Author: wprzytula

scylla-rust-wrapper/CMakeLists.txt

@@ -78,13 +78,21 @@ if(CASS_BUILD_SHARED)
 endif()
 if(CASS_BUILD_STATIC)
   cargo_build(NAME scylla_cpp_driver CRATE_TYPE staticlib
-    ENV "OPENSSL_LIB_DIR=${OPENSSL_LIB_DIR}"
+    ENV "OPENSSL_STATIC=1"
+        "OPENSSL_LIB_DIR=${OPENSSL_LIB_DIR}"
         "OPENSSL_INCLUDE_DIR=${OPENSSL_INCLUDE_DIR}")
   create_copy($<TARGET_FILE:scylla_cpp_driver_staticlib> ${INSTALL_NAME_STATIC})
   add_library(scylla-cpp-driver_static STATIC IMPORTED GLOBAL)
   add_dependencies(scylla-cpp-driver_static ${INSTALL_NAME_STATIC}_copy)
   set_target_properties(scylla-cpp-driver_static PROPERTIES IMPORTED_LOCATION ${CMAKE_BINARY_DIR}/${INSTALL_NAME_STATIC})
 endif()
+# When both builds share CARGO_TARGET_DIR, they must not run concurrently:
+# they pass different OPENSSL_STATIC values, which causes openssl-sys's build
+# script to re-run (due to rerun-if-env-changed). Concurrent cargo invocations
+# with different env fingerprints would thrash the shared build script cache.
+if(CASS_BUILD_SHARED AND CASS_BUILD_STATIC)
+  add_dependencies(scylla_cpp_driver_staticlib_target scylla_cpp_driver_cdylib_target)
+endif()
 
 #-------------------------------------
 # Installation
@@ -192,6 +200,17 @@ if(CASS_BUILD_STATIC)
   # Static library pkg-config file goes to dev package
   if(CASS_INSTALL_PKG_CONFIG)
     if(PKG_CONFIG_FOUND)
+      # System libraries needed when linking the static Rust archive.
+      # Ideally these would come from `cargo rustc -- --print native-static-libs`,
+      # but that flag is nightly-only. These are hardcoded approximations that
+      # may need updating if dependencies or Rust versions change.
+      if(APPLE)
+        set(native_static_libs "-lm -lpthread -ldl -framework Security -framework CoreFoundation")
+      elseif(WIN32)
+        set(native_static_libs "-lws2_32 -lbcrypt -luserenv -lntdll")
+      else()
+        set(native_static_libs "-lm -lpthread -ldl -lrt")
+      endif()
       configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scylla-cpp-driver_static.pc.in" "scylla-cpp-driver_static.pc" @ONLY)
       install(FILES "${CMAKE_CURRENT_BINARY_DIR}/scylla-cpp-driver_static.pc"
         DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig"

scylla-rust-wrapper/scylla-cpp-driver_static.pc.in

@@ -7,6 +7,6 @@ Name: scylla-cpp-rs-driver
 Description: ScyllaDB CPP RS Driver
 Version: @version@
 Requires.private: openssl
-Libs: -L${libdir} -lscylla-cpp-driver_static
+Libs: -L${libdir} -lscylla-cpp-driver_static @native_static_libs@
 Cflags: -I${includedir}
 URL: https://github.com/scylladb/cpp-rs-driver/