Fix Subprocess.cpp with clang + _FORTIFY_SOURCE on glibc >= 2.40#2519
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Fix Subprocess.cpp with clang + _FORTIFY_SOURCE on glibc >= 2.40#2519mszabo-wikia wants to merge 1 commit intofacebook:mainfrom
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On glibc >= 2.40, _FORTIFY_SOURCE overloads openat() when building with clang, causing the `decltype` call in Subprocess.cpp to fail since the target becomes ambiguous. So, explicitly specify our overload of choice in this case. Reproduce/test by setting `CMAKE_CXX_FLAGS=-D_FORTIFY_SOURCE=3 -DCMAKE_CXX_COMPILER=clang++`.
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Update and extend the list of hardening-related compiler flags used by HHVM to better represent modern distro defaults. * Convert the existing `ENABLE_SSP` build option into a new `ENABLE_HARDENING` option and put an updated list of security flags behind it. Both clang and GCC have been supporting these options for a while now, so we can set them irrespective of the compiler. * Put PIE-related options behind a separate `ENABLE_PIE` build option so that we can produce and compare non-PIE and PIE builds once we fix compatibility with PIE. * Forward `CMAKE_BUILD_TYPE` to vendored subprojects. Lack of this was causing the projects to be built without compiler optimizations, which doesn't play well with `FORTIFY_SOURCE`. On systems with glibc >= 2.40, facebook/folly#2519 is needed for this option to work. The overhead from these flags is likely to be limited, as many of them have been set by default for distribution packages for several years now.[1] [1] https://github.com/jvoisin/compiler-flags-distro
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Update and extend the list of hardening-related compiler flags used by HHVM to better represent modern distro defaults. * Convert the existing `ENABLE_SSP` build option into a new `ENABLE_HARDENING` option and put an updated list of security flags behind it. Both clang and GCC have been supporting these options for a while now, so we can set them irrespective of the compiler. * Put PIE-related options behind a separate `ENABLE_PIE` build option so that we can produce and compare non-PIE and PIE builds once we fix compatibility with PIE. * Forward `CMAKE_BUILD_TYPE` to vendored subprojects. Lack of this was causing the projects to be built without compiler optimizations, which doesn't play well with `FORTIFY_SOURCE`. On systems with glibc >= 2.40, facebook/folly#2519 is needed for this option to work. The overhead from these flags is likely to be limited, as many of them have been set by default for distribution packages for several years now.[1] [1] https://github.com/jvoisin/compiler-flags-distro
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Nov 25, 2025
Summary: Update and extend the list of hardening-related compiler flags used by HHVM to better represent modern distro defaults. * Convert the existing `ENABLE_SSP` build option into a new `ENABLE_HARDENING` option and put an updated list of security flags behind it. Both clang and GCC have been supporting these options for a while now, so we can set them irrespective of the compiler. * Put PIE-related options behind a separate `ENABLE_PIE` build option so that we can produce and compare non-PIE and PIE builds once we fix compatibility with PIE. * Forward `CMAKE_BUILD_TYPE` to vendored subprojects. Lack of this was causing the projects to be built without compiler optimizations, which doesn't play well with `FORTIFY_SOURCE`. On systems with glibc >= 2.40, facebook/folly#2519 is needed for this option to work. The overhead from these flags is likely to be limited, as many of them have been set by default for distribution packages for several years now.[1] [1] https://github.com/jvoisin/compiler-flags-distro Pull Request resolved: #9672 Reviewed By: Wilfred Differential Revision: D87347762 fbshipit-source-id: cdfbf29184e6022999e89258d7fa3475c971e01a
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FWIW we're seeing build failures here: and openat_2 has existed since at least glibc 2.7: https://github.com/bminor/glibc/blob/glibc-2.7/include/fcntl.h#L29 Are you sure this is correct? |
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Nov 25, 2025
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See my comment on the PR.
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So this was aiming to workaround the glibc 2.40+ changes introduced in bminor/glibc@86889e2 that only manifest with |
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On glibc >= 2.40, _FORTIFY_SOURCE overloads openat() when building with clang, causing the
decltypecall in Subprocess.cpp to fail since the target becomes ambiguous. So, explicitly specify our overload of choice in this case.Reproduce/test by setting
CMAKE_CXX_FLAGS=-D_FORTIFY_SOURCE=3 -DCMAKE_CXX_COMPILER=clang++.