Generate native glibc.modulemap when cross-compiling

Author: springsup

stdlib/public/Platform/CMakeLists.txt

@@ -38,23 +38,24 @@ foreach(sdk ${SWIFT_SDKS})
       set(arch_subdir "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${arch}")
       set(module_dir "${SWIFTLIB_DIR}/${arch_subdir}")
 
-      # Determine the location of glibc based on the target.
+      # Determine the location of glibc headers based on the target.
+      set(GLIBC_NATIVE_INCLUDE_PATH "/usr/include")
+      set(GLIBC_NATIVE_ARCH_INCLUDE_PATH ${GLIBC_NATIVE_INCLUDE_PATH})
+      # Some SDKs place their headers in architecture-specific subfolders.
+      if((${sdk} STREQUAL "LINUX" OR ${sdk} STREQUAL "FREEBSD") AND CMAKE_LIBRARY_ARCHITECTURE)
+        set(GLIBC_NATIVE_ARCH_INCLUDE_PATH "${GLIBC_NATIVE_ARCH_INCLUDE_PATH}/${CMAKE_LIBRARY_ARCHITECTURE}")
+      endif()
+
+      # Android uses a different sysroot variable, although there are pending PRs to refactor this
       if(${sdk} STREQUAL "ANDROID")
-        set(GLIBC_INCLUDE_PATH "${SWIFT_ANDROID_SDK_PATH}/usr/include")
-        set(GLIBC_ARCH_INCLUDE_PATH ${GLIBC_INCLUDE_PATH})
+        set(GLIBC_SYSTEM_ROOT "${SWIFT_ANDROID_SDK_PATH}")
       else()
-        set(GLIBC_INCLUDE_PATH "/usr/include")
-        set(GLIBC_ARCH_INCLUDE_PATH ${GLIBC_INCLUDE_PATH})
-        if((${sdk} STREQUAL "LINUX" OR ${sdk} STREQUAL "FREEBSD") AND CMAKE_LIBRARY_ARCHITECTURE)
-          # FIXME: Some distributions install headers in
-          #        "/usr/include/x86_64-linux-gnu/sys/...". Here we use the host
-          #        machine's path, regardless of the SDK target we're building for.
-          #        This will break if cross-compiling from a distro that uses the
-          #        architecture as part of the path to a distro that does not.
-          set(GLIBC_ARCH_INCLUDE_PATH "${GLIBC_INCLUDE_PATH}/${CMAKE_LIBRARY_ARCHITECTURE}")
-        endif()
+        set(GLIBC_SYSTEM_ROOT "${CMAKE_SYSROOT}")
       endif()
 
+      set(GLIBC_INCLUDE_PATH "${GLIBC_SYSTEM_ROOT}/${GLIBC_NATIVE_INCLUDE_PATH}")
+      set(GLIBC_ARCH_INCLUDE_PATH ${GLIBC_SYSTEM_ROOT}/${GLIBC_NATIVE_ARCH_INCLUDE_PATH})
+
       set(glibc_modulemap_source "glibc.modulemap.gyb")
       set(glibc_modulemap_out "${module_dir}/glibc.modulemap")
 
@@ -68,11 +69,28 @@ foreach(sdk ${SWIFT_SDKS})
               "-DGLIBC_INCLUDE_PATH=${GLIBC_INCLUDE_PATH}"
               "-DGLIBC_ARCH_INCLUDE_PATH=${GLIBC_ARCH_INCLUDE_PATH}")
 
+      list(APPEND glibc_modulemap_target_list ${glibc_modulemap_target})
+
+      # If cross-compiling, generate a native modulemap without the sysroot prefix
+      # The prefixed one is still the 'glibc.modulemap' which we'll look at during the build process
+      if(CMAKE_CROSSCOMPILING)
+        set(glibc_native_modulemap_out "${module_dir}/native-substitutes/glibc.modulemap")
+        handle_gyb_source_single(glibc_modulemap_native_target
+            SOURCE "${glibc_modulemap_source}"
+            OUTPUT "${glibc_native_modulemap_out}"
+            FLAGS
+                "-DCMAKE_SDK=${sdk}"
+                "-DGLIBC_INCLUDE_PATH=${GLIBC_NATIVE_INCLUDE_PATH}"
+                "-DGLIBC_ARCH_INCLUDE_PATH=${GLIBC_NATIVE_ARCH_INCLUDE_PATH}")
+
+        list(APPEND glibc_modulemap_target_list ${glibc_modulemap_native_target})
+        set(glibc_modulemap_out ${glibc_native_modulemap_out})
+      endif()
+        
       swift_install_in_component(sdk-overlay
           FILES "${glibc_modulemap_out}"
           DESTINATION "lib/swift/${arch_subdir}")
 
-      list(APPEND glibc_modulemap_target_list ${glibc_modulemap_target})
     endforeach()
   endif()
 endforeach()