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[libc] Handle the unknown default target in CMake #115122

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Merged
merged 1 commit into from
Nov 12, 2025
Merged

[libc] Handle the unknown default target in CMake #115122

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65 changes: 31 additions & 34 deletions libc/cmake/modules/LLVMLibCArchitectures.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -94,17 +94,6 @@ if(NOT libc_compiler_target_info)
endif()
string(STRIP ${libc_compiler_target_info} libc_compiler_target_info)
string(SUBSTRING ${libc_compiler_target_info} 8 -1 libc_compiler_triple)
get_arch_and_system_from_triple(${libc_compiler_triple}
compiler_arch compiler_sys)
if(NOT compiler_arch)
message(FATAL_ERROR
"libc build: Invalid or unknown libc compiler target triple: "
"${libc_compiler_triple}")
endif()

set(LIBC_TARGET_ARCHITECTURE ${compiler_arch})
set(LIBC_TARGET_OS ${compiler_sys})
set(LIBC_CROSSBUILD FALSE)

# One should not set LLVM_RUNTIMES_TARGET and LIBC_TARGET_TRIPLE
if(LLVM_RUNTIMES_TARGET AND LIBC_TARGET_TRIPLE)
Expand All @@ -128,12 +117,40 @@ endif()
# architecture.
if(explicit_target_triple)
get_arch_and_system_from_triple(${explicit_target_triple} libc_arch libc_sys)
if(NOT libc_arch)
if(NOT libc_arch OR NOT libc_sys)
message(FATAL_ERROR
"libc build: Invalid or unknown triple: ${explicit_target_triple}")
endif()
set(LIBC_TARGET_ARCHITECTURE ${libc_arch})
set(LIBC_TARGET_OS ${libc_sys})
# If the compiler target triple is not the same as the triple specified by
# LIBC_TARGET_TRIPLE or LLVM_RUNTIMES_TARGET, we will add a --target option
# if the compiler is clang. If the compiler is GCC we just error out as there
# is no equivalent of an option like --target.
if(NOT libc_compiler_triple STREQUAL explicit_target_triple)
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@lntue lntue Nov 6, 2024

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libc_compiler_triple is not obtained before this anymore, so it means that it is always crossbuild whenever target triple is specified?

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@petrhosek petrhosek Nov 12, 2025

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libc_compiler_triple is set on line 96.

set(LIBC_CROSSBUILD TRUE)
if(CMAKE_COMPILER_IS_GNUCXX)
message(FATAL_ERROR
"GCC target triple (${libc_compiler_triple}) and the explicity "
"specified target triple (${explicit_target_triple}) do not match.")
else()
list(APPEND
LIBC_COMPILE_OPTIONS_DEFAULT "--target=${explicit_target_triple}")
endif()
else()
set(LIBC_CROSSBUILD FALSE)
endif()
else()
get_arch_and_system_from_triple(${libc_compiler_triple}
compiler_arch compiler_sys)
if(NOT compiler_arch OR NOT compiler_sys)
message(FATAL_ERROR
"libc build: Unknown compiler default target triple: "
"${libc_compiler_triple}")
endif()
set(LIBC_TARGET_ARCHITECTURE ${compiler_arch})
set(LIBC_TARGET_OS ${compiler_sys})
set(LIBC_CROSSBUILD FALSE)
endif()

if((LIBC_TARGET_OS STREQUAL "unknown") OR (LIBC_TARGET_OS STREQUAL "none"))
Expand Down Expand Up @@ -198,31 +215,11 @@ else()
"Unsupported libc target operating system ${LIBC_TARGET_OS}")
endif()


# If the compiler target triple is not the same as the triple specified by
# LIBC_TARGET_TRIPLE or LLVM_RUNTIMES_TARGET, we will add a --target option
# if the compiler is clang. If the compiler is GCC we just error out as there
# is no equivalent of an option like --target.
if(explicit_target_triple AND
(NOT (libc_compiler_triple STREQUAL explicit_target_triple)))
set(LIBC_CROSSBUILD TRUE)
if(CMAKE_COMPILER_IS_GNUCXX)
message(FATAL_ERROR
"GCC target triple (${libc_compiler_triple}) and the explicity "
"specified target triple (${explicit_target_triple}) do not match.")
else()
list(APPEND
LIBC_COMPILE_OPTIONS_DEFAULT "--target=${explicit_target_triple}")
endif()
endif()


# Windows does not support full mode build.
if (LIBC_TARGET_OS_IS_WINDOWS AND LLVM_LIBC_FULL_BUILD)
message(FATAL_ERROR "Windows does not support full mode build.")
endif ()


message(STATUS
"Building libc for ${LIBC_TARGET_ARCHITECTURE} on ${LIBC_TARGET_OS} with
LIBC_COMPILE_OPTIONS_DEFAULT: ${LIBC_COMPILE_OPTIONS_DEFAULT}")
"Building libc for ${LIBC_TARGET_ARCHITECTURE} on ${LIBC_TARGET_OS} with "
"LIBC_COMPILE_OPTIONS_DEFAULT: ${LIBC_COMPILE_OPTIONS_DEFAULT}")
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