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[flang-rt][build] Add support for building flang-rt as a standalone project #168321

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[flang-rt][build] Add support for building flang-rt as a standalone project #168321

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20 changes: 20 additions & 0 deletions flang-rt/.gitignore
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
Debug
Release
MinSizeRel
build
root
tags
TAGS
.nfs*
*.sw?
*~
*#
CMakeCache.txt
*/CMakeFiles/*
*/*/CMakeFiles/*
*/Makefile
*/*/Makefile
cmake_install.cmake
formatted
.DS_Store
.vs_code
13 changes: 10 additions & 3 deletions flang-rt/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
# included using the LLVM_ENABLE_RUNTIMES mechanism.
#
#===------------------------------------------------------------------------===#

cmake_minimum_required(VERSION 3.20.0)
if (NOT LLVM_RUNTIMES_BUILD)
message(FATAL_ERROR "Use this CMakeLists.txt from LLVM's runtimes build system.
Example:
Expand Down Expand Up @@ -54,13 +54,16 @@ if (CMAKE_VERSION VERSION_LESS "3.24")
set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
endif ()
else ()
set(CMAKE_Fortran_COMPILER_FORCED ON)
endif ()
enable_language(Fortran)


list(APPEND CMAKE_MODULE_PATH
"${FLANG_RT_SOURCE_DIR}/cmake/modules"
"${FLANG_SOURCE_DIR}/cmake/modules"
"${FLANG_SOURCE_DIR}/../cmake/Modules"
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@Meinersbur Meinersbur Nov 19, 2025

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This path is already inserted by https://github.com/llvm/llvm-project/blob/main/runtimes/CMakeLists.txt#L30

)
include(AddFlangRT)
include(GetToolchainDirs)
Expand Down Expand Up @@ -142,12 +145,14 @@ option(FLANG_RT_INCLUDE_TESTS "Generate build targets for the flang-rt unit and
# Provide an interface to link against the LLVM libc/libc++ projects directly.
set(FLANG_RT_SUPPORTED_PROVIDERS system llvm)
set(FLANG_RT_LIBC_PROVIDER "system" CACHE STRING "Specify C library to use. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
if (NOT "${FLANG_RT_LIBC_PROVIDER}" IN_LIST FLANG_RT_SUPPORTED_PROVIDERS)
list(FIND FLANG_RT_SUPPORTED_PROVIDERS "${FLANG_RT_LIBC_PROVIDER}" libc_index)
if (libc_index EQUAL -1)
message(FATAL_ERROR "Unsupported library: '${FLANG_RT_RUNTIME_PROVIDER}'. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
endif ()

set(FLANG_RT_LIBCXX_PROVIDER "system" CACHE STRING "Specify C++ library to use. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
if (NOT "${FLANG_RT_LIBCXX_PROVIDER}" IN_LIST FLANG_RT_SUPPORTED_PROVIDERS)
list(FIND FLANG_RT_SUPPORTED_PROVIDERS "${FLANG_RT_LIBCXX_PROVIDER}" libcxx_index)
if (libcxx_index EQUAL -1)
message(FATAL_ERROR "Unsupported library: '${FLANG_RT_LIBCXX_PROVIDER}'. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
endif ()

Expand Down Expand Up @@ -250,6 +255,8 @@ endif ()
# Aternatively, we could use
# CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU"
# but some older versions of CMake don't define it for GCC itself.
include(CheckCXXCompilerFlag)
include(CheckLinkerFlag)
check_cxx_compiler_flag("-Wp,-UTESTFLAG" FLANG_RT_SUPPORTS_UNDEFINE_FLAG)

# Check whether -fno-lto is supported.
Expand Down