forked from OSchip/llvm-project
60 lines
2.6 KiB
C
60 lines
2.6 KiB
C
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//===-- sanitizer_win_defs.h ------------------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Common definitions for Windows-specific code.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SANITIZER_WIN_DEFS_H
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#define SANITIZER_WIN_DEFS_H
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#include "sanitizer_platform.h"
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#if SANITIZER_WINDOWS
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#if defined(_WIN64)
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#define WIN_SYM_PREFIX
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#else
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#define WIN_SYM_PREFIX "_"
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#endif
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// Intermediate macro to ensure the parameter is expanded before stringified.
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#define STRINGIFY(A) #A
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// ----------------- A workaround for the absence of weak symbols --------------
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// We don't have a direct equivalent of weak symbols when using MSVC, but we can
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// use the /alternatename directive to tell the linker to default a specific
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// symbol to a specific value.
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// Take into account that the function will be marked as UNDEF in the symbol
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// table of the resulting object file, even if we provided a default value, and
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// the linker won't find the default implementation until it links with that
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// object file.
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// So, suppose we provide a default implementation "fundef" for "fun", and this
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// is compiled into the object file "test.obj".
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// If we have some code with references to "fun" and we link that code with
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// "test.obj", it will work because the linker always link object files.
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// But, if "test.obj" is included in a static library, like "test.lib", then the
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// liker will only link to "test.obj" if necessary. If we only included the
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// definition of "fun", it won't link to "test.obj" (from test.lib) because
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// "fun" appears as UNDEF, so it doesn't resolve the symbol "fun", and this will
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// result in a link error.
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// So, a workaround is to force linkage with the modules that include weak
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// definitions, with the following macro: WIN_FORCE_LINK()
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#define WIN_WEAK_ALIAS_(Name, Default) \
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__pragma(comment(linker, "/alternatename:" WIN_SYM_PREFIX STRINGIFY(Name) "="\
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WIN_SYM_PREFIX STRINGIFY(Default)))
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#define WIN_WEAK_ALIAS(Name, Default) \
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WIN_WEAK_ALIAS_(Name, Default)
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#define WIN_FORCE_LINK(Name) \
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__pragma(comment(linker, "/include:" WIN_SYM_PREFIX STRINGIFY(Name)))
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#endif // SANITIZER_WINDOWS
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#endif // SANITIZER_WIN_DEFS_H
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