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[CMake] Windows stdlib cross-compilation fixes #13140

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Merged
merged 2 commits into from
Apr 18, 2018
Merged

[CMake] Windows stdlib cross-compilation fixes #13140

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7c2230b
Fix cross-compilation for the Windows stdlib
troughton Jan 31, 2018
5173e3c
SwiftPrivate now builds on Windows with Pull-14710
troughton Feb 20, 2018
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14 changes: 14 additions & 0 deletions cmake/modules/AddSwift.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -734,6 +734,7 @@ function(_add_swift_library_single target name)
swift_windows_generate_sdk_vfs_overlay(SWIFTLIB_SINGLE_VFS_OVERLAY_FLAGS)
foreach(flag ${SWIFTLIB_SINGLE_VFS_OVERLAY_FLAGS})
list(APPEND SWIFTLIB_SINGLE_SWIFT_COMPILE_FLAGS -Xcc;${flag})
list(APPEND SWIFTLIB_SINGLE_C_COMPILE_FLAGS ${flag})
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What is this for?

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Windows is case-insensitive, so when you're cross-compiling from a case-sensitive filesystem a number of header paths don't resolve (since the Windows headers are very loose about case and the spellings vary between files).

The VFS overlay is a means to map between the differently-cased forms of the headers (e.g. windows.h to Windows.h). Previously, it wasn't passing the argument to use the VFS overlay to the C/C++ runtime sources correctly (so it was working for Swift import Msvcrt only).

endforeach()
foreach(directory ${SWIFTLIB_INCLUDE})
list(APPEND SWIFTLIB_SINGLE_SWIFT_COMPILE_FLAGS -Xfrontend;-I${directory})
Expand Down Expand Up @@ -1613,6 +1614,19 @@ function(add_swift_library name)
endif()
endif()

# We unconditionally removed "-z,defs" from CMAKE_SHARED_LINKER_FLAGS in
# swift_common_standalone_build_config_llvm within SwiftSharedCMakeConfig.cmake,
# where it was added by a call to HandleLLVMOptions.
#
# Rather than applying it to all targets and libraries, we here add it back to
# supported targets and libraries only.
# This is needed for ELF targets only; however, RemoteMirror needs to build
# with undefined symbols.
if("${SWIFT_SDK_${LFLAGS_SDK}_OBJECT_FORMAT}" STREQUAL "ELF"
AND NOT "${name}" STREQUAL "swiftRemoteMirror")
list(APPEND swiftlib_link_flags_all "-Wl,-z,defs")
endif()

# Add this library variant.
_add_swift_library_single(
${VARIANT_NAME}
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14 changes: 11 additions & 3 deletions cmake/modules/SwiftSharedCMakeConfig.cmake
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Expand Up @@ -78,9 +78,17 @@ macro(swift_common_standalone_build_config_llvm product is_cross_compiling)
include(AddSwiftTableGen) # This imports TableGen from LLVM.
include(HandleLLVMOptions)

# HACK: this ugly tweaking is to prevent the propagation of the flag from LLVM
# into swift. The use of this flag pollutes all targets, and we are not able
# to remove it on a per-target basis which breaks cross-compilation.
# HACK: Not all targets support -z,defs as a linker flag.
#
# Normally, LLVM would only add it as an option for known ELF targets;
# however, due to the custom scheme Swift uses for cross-compilation, the
# CMAKE_SHARED_LINKER_FLAGS are determined based on the host system and
# then applied to all targets. This causes issues in cross-compiling to
# Windows from a Linux host.
#
# To work around this, we unconditionally remove the flag here and then
# selectively add it to the per-target link flags; this is currently done
# in add_swift_library within AddSwift.cmake.
string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")

set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
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3 changes: 0 additions & 3 deletions stdlib/public/SwiftRemoteMirror/CMakeLists.txt
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@@ -1,6 +1,3 @@
# HACK: Force this library to build with undefined symbols.
string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")

# libswiftRemoteMirror.dylib should not have runtime dependencies; it's
# always built as a shared library.
if(SWIFT_BUILD_DYNAMIC_STDLIB OR SWIFT_BUILD_REMOTE_MIRROR)
Expand Down