53 lines
2.3 KiB
Diff
53 lines
2.3 KiB
Diff
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commit 7ed4745a092a203f92fc37ab5894e92117db0c94
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Author: Austin Seipp <aseipp@pobox.com>
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Date: Sat May 4 15:23:35 2019 -0500
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flow: fix a build failure with Clang/libcxx on Linux
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11bd7d7da introduced a hack on Linux to work around a missing symbol in
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libstdc++'s _pic library on Ubuntu. Unfortunately, this causes the build
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to fail when using Clang, as it doesn't believe this symbol is part of
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its headers in c++11 mode.
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Unfortunately there's no good way to distinguish libcxx from libstdc++
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with the preprocessor, so we merely gate it by only checking for clang,
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iff we are on Linux.
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With this change, Clang 8.x can build FoundationDB on Linux using libcxx
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as the standard C++ library.
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Signed-off-by: Austin Seipp <aseipp@pobox.com>
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diff --git a/flow/Platform.cpp b/flow/Platform.cpp
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index 3d3f1ac0..9f21dfd4 100644
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--- a/flow/Platform.cpp
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+++ b/flow/Platform.cpp
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@@ -2841,13 +2841,26 @@ void setupSlowTaskProfiler() {
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#endif
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}
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-#ifdef __linux__
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+#if defined(__linux__) && !defined(__clang__)
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// There's no good place to put this, so it's here.
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// Ubuntu's packaging of libstdc++_pic offers different symbols than libstdc++. Go figure.
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// Notably, it's missing a definition of std::istream::ignore(long), which causes compilation errors
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// in the bindings. Thus, we provide weak versions of their definitions, so that if the
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// linked-against libstdc++ is missing their definitions, we'll be able to use the provided
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// ignore(long, int) version.
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+//
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+// Note that this hack is DISABLED when we use Clang. It is only needed when we statically link
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+// to the _pic libraries, but only official FDB Linux binaries are built this way using GCC. If we
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+// don't use the _pic libraries, then this hack is entirely unneeded -- likely the case when using
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+// Clang on Linux.
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+//
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+// Doing this allows us to use LLVM's libc++ with Clang on Linux -- otherwise, providing
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+// a weak symbol definition for an internal (non-public) class member fails (due to that member
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+// being non-existant on libc++.) See upstream GitHub issue #1533 for more information.
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+//
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+// TODO FIXME: Obliterate this when the official build environment is upgraded beyond Ubuntu 14.04.
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+// (This problem should be fixed in later LTS releases.)
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+
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#include <istream>
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namespace std {
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typedef basic_istream<char, std::char_traits<char>> char_basic_istream;
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