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[Cxx] Make C++ flags configurable for Linux SDK #59764

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Merged
merged 1 commit into from
Jun 29, 2022
Merged

[Cxx] Make C++ flags configurable for Linux SDK #59764

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15 changes: 15 additions & 0 deletions cmake/modules/SwiftConfigureSDK.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -282,6 +282,21 @@ macro(configure_sdk_unix name architectures)
endif()
set(SWIFT_SDK_${prefix}_USE_ISYSROOT FALSE)

# GCC on Linux is usually located under `/usr`.
# However, Ubuntu 20.04 ships with another GCC installation under `/`, which
# does not include libstdc++. Swift build scripts pass `--sysroot=/` to
# Clang. By default, Clang tries to find GCC installation under sysroot, and
# if it doesn't exist, under `{sysroot}/usr`. On Ubuntu 20.04 and newer, it
# attempts to use the GCC without the C++ stdlib, which causes a build
# failure. To fix that, we tell Clang explicitly to use GCC from `/usr`.
# FIXME: This is a compromise. The value might depend on the architecture
# but add_swift_target_library does not allow passing different values
# depending on the architecture, so having a single value is the only
# possibility right now.
set(SWIFT_SDK_${prefix}_CXX_OVERLAY_SWIFT_COMPILE_FLAGS
-Xcc --gcc-toolchain=/usr
CACHE STRING "Extra flags for compiling the C++ overlay")

foreach(arch ${architectures})
if("${prefix}" STREQUAL "ANDROID")
swift_android_sysroot(android_sysroot)
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7 changes: 1 addition & 6 deletions stdlib/public/Cxx/std/CMakeLists.txt
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Expand Up @@ -143,12 +143,7 @@ add_swift_target_library(swiftstd ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_SDK_OVE
-Xfrontend -module-interface-preserve-types-as-written

SWIFT_COMPILE_FLAGS_LINUX
# GCC on Linux is usually located under `/usr`.
# However, Ubuntu 20.04 ships with another GCC installation under `/`, which does not include libstdc++.
# Swift build scripts pass `--sysroot=/` to Clang. By default, Clang tries to find GCC installation under sysroot,
# and if it doesn't exist, under `{sysroot}/usr`. On Ubuntu 20.04 and newer, it attempts to use the GCC without the
# C++ stdlib, which causes a build failure. To fix that, we tell Clang explicitly to use GCC from `/usr`.
-Xcc --gcc-toolchain=/usr
${SWIFT_SDK_LINUX_CXX_OVERLAY_SWIFT_COMPILE_FLAGS}

LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
TARGET_SDKS ALL_APPLE_PLATFORMS LINUX
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