3fb092979e
GCC 13 is more strict about what C++ features are available in a freestanding (= build without standard library) build. The `stdlib.h` and `math.h` headers are redefined as part of libstdc++. If the object is built as freestanding, it should be assumed that none of the standard library functions are available. The solution in Haiku has been to add part of the standard library into the kernel shared object. The method of exposing them has been to allow the use of `stdlib.h` and `math.h` in the kernel and in kernel add-ons. This change allows that approach to continue. What it does, is that it defines specific headers which will be picked up when a module is built using private kernel headers. When building for the kernel (or for the boot module), it will bypass GCC 13's libstdc++ default behaviour of not including the POSIX/platform header with all the function definitions. An alternative to be considered for the longer term is to specifically define the parts of the C/C++ standard library that is available in the kernel in these headers, or create custom headers when building kernel modules (which is how Linux approaches it). Change-Id: Icab4614f642219fa77732b02401570708ee9a963 Reviewed-on: https://review.haiku-os.org/c/haiku/+/6645 Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
34 lines
1.2 KiB
C
34 lines
1.2 KiB
C
/*
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* Copyright 2023, Haiku Inc. All Rights Reserved.
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* Distributed under the terms of the MIT License.
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*/
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#ifndef _KERNEL_MATH_H
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#define _KERNEL_MATH_H
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/*
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When building the kernel, the bootloader or kernel add-ons, the Haiku build system passes the
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`-ffreestanding` argument to GCC, in order to make sure that only the C++ language features can
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be used that do not require the C/C++ standard library.
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The Haiku kernel and boot loaders include part of the standard library in the kernel/boot
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loader. It uses the C/C++ standard library headers (like this one) to expose the
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functions/features that are available in the kernel/boot loader.
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If we are building for the kernel or the boot loader, the logic below will tell GCC's C++
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headers to include the underlying posix headers, so that the kernel, the boot loader and kernel
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add-ons can link to the symbols defined in them.
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When we are NOT building for the kernel or the boot loader, we fall back to GCC's default
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behaviour.
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*/
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#if (defined(_KERNEL_MODE) || defined(_BOOT_MODE)) && !defined(_GLIBCXX_INCLUDE_NEXT_C_HEADERS)
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# define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
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# include_next <math.h>
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# undef _GLIBCXX_INCLUDE_NEXT_C_HEADERS
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#else
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# include_next <math.h>
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#endif
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#endif // _KERNEL_MATH_H
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