[libc] Include Linux kernel headers in the full build #97486
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When doing a full build for Linux, as of llvm#97461 we no longer include system headers, but we need to include Linux kernel headers.
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@llvm/pr-subscribers-libc Author: Petr Hosek (petrhosek) ChangesWhen doing a full build for Linux, as of #97461 we no longer include system headers, but we need to include Linux kernel headers. Full diff: https://github.com/llvm/llvm-project/pull/97486.diff 2 Files Affected:
diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 4ffcd55ba9500..013b17b03f570 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -39,6 +39,8 @@ set(LIBC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR})
set(LIBC_ENABLE_USE_BY_CLANG OFF CACHE BOOL "Whether or not to place libc in a build directory findable by a just built clang")
+set(LIBC_KERNEL_HEADERS "/usr/include" CACHE STRING "Path to Linux kernel headers")
+
# Defining a global namespace to enclose all libc functions.
set(default_namespace "__llvm_libc")
if(LLVM_VERSION_MAJOR)
diff --git a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
index 28379213029a3..d6a8764c3de16 100644
--- a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
+++ b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
@@ -54,6 +54,9 @@ function(_get_common_compile_options output_var flags)
list(APPEND compile_options "-isystem${COMPILER_RESOURCE_DIR}/include")
list(APPEND compile_options "-nostdinc")
endif()
+ if(LIBC_TARGET_OS_IS_LINUX)
+ list(APPEND compile_options "-idirafter${LIBC_KERNEL_HEADERS}")
+ endif()
endif()
if(LIBC_COMPILER_HAS_FIXED_POINT)
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frobtech
approved these changes
Jul 2, 2024
| @@ -54,6 +54,9 @@ function(_get_common_compile_options output_var flags) | |||
| list(APPEND compile_options "-isystem${COMPILER_RESOURCE_DIR}/include") | |||
| list(APPEND compile_options "-nostdinc") | |||
| endif() | |||
| if(LIBC_TARGET_OS_IS_LINUX) | |||
| list(APPEND compile_options "-idirafter${LIBC_KERNEL_HEADERS}") | |||
There was a problem hiding this comment.
It merits a comment about why we want to use -idirafter, which is in case it's a directory like /usr/include that might contain other headers that we don't want to risk preempting libc's own headers.
michaelrj-google
approved these changes
Jul 2, 2024
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@frobtech Should we add this flag this unconditionally or only when |
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I'm going to merge this to fix the buildbots for now. Feel free to create followup patches. |
lravenclaw
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Jul 3, 2024
When doing a full build for Linux, as of llvm#97461 we no longer include system headers, but we need to include Linux kernel headers.
kbluck
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Jul 6, 2024
When doing a full build for Linux, as of llvm#97461 we no longer include system headers, but we need to include Linux kernel headers.
mikhailramalho
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Jul 19, 2024
When crosscompiling, we need to search for the linux kernel headers in the sysroot but since llvm#97486 the linux kernel headers were always searched in /usr/include. This patch fixes this behaviour by prepending a '=' to where we search for the kernel headers. As per the gcc/clang's documentation a '=' before the path is replaced by the sysroot.
mikhailramalho
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Jul 19, 2024
#99588) When crosscompiling, we need to search for the linux kernel headers in the sysroot but since #97486 the linux kernel headers were always searched in /usr/include. This patch fixes this behaviour by prepending a '=' to where we search for the kernel headers. As per the gcc/clang's documentation a '=' before the path is replaced by the sysroot. This patch also includes a fix for rv32, that fails to compile due to a missing definition of CLOCK_REALTIME after this change.
sgundapa
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Jul 23, 2024
llvm#99588) When crosscompiling, we need to search for the linux kernel headers in the sysroot but since llvm#97486 the linux kernel headers were always searched in /usr/include. This patch fixes this behaviour by prepending a '=' to where we search for the kernel headers. As per the gcc/clang's documentation a '=' before the path is replaced by the sysroot. This patch also includes a fix for rv32, that fails to compile due to a missing definition of CLOCK_REALTIME after this change.
yuxuanchen1997
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Jul 25, 2024
#99588) Summary: When crosscompiling, we need to search for the linux kernel headers in the sysroot but since #97486 the linux kernel headers were always searched in /usr/include. This patch fixes this behaviour by prepending a '=' to where we search for the kernel headers. As per the gcc/clang's documentation a '=' before the path is replaced by the sysroot. This patch also includes a fix for rv32, that fails to compile due to a missing definition of CLOCK_REALTIME after this change. Test Plan: Reviewers: Subscribers: Tasks: Tags: Differential Revision: https://phabricator.intern.facebook.com/D60251638
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So to be more hermetic, I'd like to get to the point where we encourage the user to build the kernel headers from source BEFORE building llvm-libc, then provide those headers. That way we don't look in /usr/include AT ALL. For example, I'm not sure that the kernel headers on the host are ok to use when cross compiling. |
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When doing a full build for Linux, as of #97461 we no longer include system headers, but we need to include Linux kernel headers.