229 lines
6.3 KiB
C++
229 lines
6.3 KiB
C++
// Copyright The OpenTelemetry Authors
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// SPDX-License-Identifier: Apache-2.0
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#pragma once
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#if !defined(OPENTELEMETRY_LIKELY_IF) && defined(__cplusplus)
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// GCC 9 has likely attribute but do not support declare it at the beginning of statement
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# if defined(__has_cpp_attribute) && (defined(__clang__) || !defined(__GNUC__) || __GNUC__ > 9)
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# if __has_cpp_attribute(likely)
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# define OPENTELEMETRY_LIKELY_IF(...) \
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if (__VA_ARGS__) \
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[[likely]]
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# endif
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# endif
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#endif
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#if !defined(OPENTELEMETRY_LIKELY_IF) && (defined(__clang__) || defined(__GNUC__))
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# define OPENTELEMETRY_LIKELY_IF(...) if (__builtin_expect(!!(__VA_ARGS__), true))
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#endif
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#ifndef OPENTELEMETRY_LIKELY_IF
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# define OPENTELEMETRY_LIKELY_IF(...) if (__VA_ARGS__)
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#endif
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/// \brief Declare variable as maybe unused
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/// usage:
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/// OPENTELEMETRY_MAYBE_UNUSED int a;
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/// class OPENTELEMETRY_MAYBE_UNUSED a;
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/// OPENTELEMETRY_MAYBE_UNUSED int a();
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///
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#if defined(__cplusplus) && __cplusplus >= 201703L
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# define OPENTELEMETRY_MAYBE_UNUSED [[maybe_unused]]
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#elif defined(__clang__)
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# define OPENTELEMETRY_MAYBE_UNUSED __attribute__((unused))
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#elif defined(__GNUC__) && ((__GNUC__ >= 4) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 1)))
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# define OPENTELEMETRY_MAYBE_UNUSED __attribute__((unused))
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#elif (defined(_MSC_VER) && _MSC_VER >= 1910) && (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
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# define OPENTELEMETRY_MAYBE_UNUSED [[maybe_unused]]
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#else
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# define OPENTELEMETRY_MAYBE_UNUSED
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#endif
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#ifndef OPENTELEMETRY_RTTI_ENABLED
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# if defined(__clang__)
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# if __has_feature(cxx_rtti)
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# define OPENTELEMETRY_RTTI_ENABLED
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# endif
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# elif defined(__GNUG__)
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# if defined(__GXX_RTTI)
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# define OPENTELEMETRY_RTTI_ENABLED
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# endif
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# elif defined(_MSC_VER)
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# if defined(_CPPRTTI)
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# define OPENTELEMETRY_RTTI_ENABLED
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# endif
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# endif
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#endif
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#if defined(__cplusplus) && __cplusplus >= 201402L
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# define OPENTELEMETRY_DEPRECATED [[deprecated]]
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#elif defined(__clang__)
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# define OPENTELEMETRY_DEPRECATED __attribute__((deprecated))
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#elif defined(__GNUC__)
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# define OPENTELEMETRY_DEPRECATED __attribute__((deprecated))
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#elif defined(_MSC_VER)
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# if _MSC_VER >= 1910 && defined(_MSVC_LANG) && _MSVC_LANG >= 201703L
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# define OPENTELEMETRY_DEPRECATED [[deprecated]]
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# else
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# define OPENTELEMETRY_DEPRECATED __declspec(deprecated)
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# endif
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#else
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# define OPENTELEMETRY_DEPRECATED
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#endif
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#if defined(__cplusplus) && __cplusplus >= 201402L
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg) [[deprecated(msg)]]
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#elif defined(__clang__)
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg) __attribute__((deprecated(msg)))
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#elif defined(__GNUC__)
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg) __attribute__((deprecated(msg)))
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#elif defined(_MSC_VER)
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# if _MSC_VER >= 1910 && defined(_MSVC_LANG) && _MSVC_LANG >= 201703L
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg) [[deprecated(msg)]]
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# else
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg) __declspec(deprecated(msg))
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# endif
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#else
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# define OPENTELEMETRY_DEPRECATED_MESSAGE(msg)
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#endif
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// Regex support
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#if (__GNUC__ == 4 && (__GNUC_MINOR__ == 8 || __GNUC_MINOR__ == 9))
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# define OPENTELEMETRY_HAVE_WORKING_REGEX 0
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#else
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# define OPENTELEMETRY_HAVE_WORKING_REGEX 1
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#endif
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/* clang-format off */
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/**
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@page HEADER_ONLY_SINGLETON Header only singleton.
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@section ELF_SINGLETON
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For clang and gcc, the desired coding pattern is as follows.
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@verbatim
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class Foo
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{
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// (a)
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__attribute__((visibility("default")))
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// (b)
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T& get_singleton()
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{
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// (c)
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static T singleton;
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return singleton;
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}
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};
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@endverbatim
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(a) is needed when the code is build with
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@code -fvisibility="hidden" @endcode
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to ensure that all instances of (b) are visible to the linker.
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What is duplicated in the binary is @em code, in (b).
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The linker will make sure only one instance
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of all the (b) methods is used.
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(c) is a singleton implemented inside a method.
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This is very desirable, because:
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- the C++ compiler guarantees that construction
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of the variable (c) is thread safe.
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- constructors for (c) singletons are executed in code path order,
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or not at all if the singleton is never used.
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@section OTHER_SINGLETON
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For other platforms, header only singletons are not supported at this
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point.
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@section CODING_PATTERN
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The coding pattern to use in the source code is as follows
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@verbatim
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class Foo
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{
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OPENTELEMETRY_API_SINGLETON
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T& get_singleton()
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{
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static T singleton;
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return singleton;
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}
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};
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@endverbatim
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*/
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/* clang-format on */
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#if defined(__clang__)
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# define OPENTELEMETRY_API_SINGLETON __attribute__((visibility("default")))
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#elif defined(__GNUC__)
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# define OPENTELEMETRY_API_SINGLETON __attribute__((visibility("default")))
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#else
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/* Add support for other compilers here. */
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# define OPENTELEMETRY_API_SINGLETON
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#endif
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//
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// Atomic wrappers based on compiler intrinsics for memory read/write.
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// The tailing number is read/write length in bits.
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//
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// N.B. Compiler instrinsic is used because the usage of C++ standard library is restricted in the
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// OpenTelemetry C++ API.
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//
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#if defined(__GNUC__)
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# define OPENTELEMETRY_ATOMIC_READ_8(ptr) __atomic_load_n(ptr, __ATOMIC_SEQ_CST)
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# define OPENTELEMETRY_ATOMIC_WRITE_8(ptr, value) __atomic_store_n(ptr, value, __ATOMIC_SEQ_CST)
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#elif defined(_MSC_VER)
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# include <intrin.h>
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# define OPENTELEMETRY_ATOMIC_READ_8(ptr) \
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static_cast<uint8_t>(_InterlockedCompareExchange8(reinterpret_cast<char *>(ptr), 0, 0))
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# define OPENTELEMETRY_ATOMIC_WRITE_8(ptr, value) \
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_InterlockedExchange8(reinterpret_cast<char *>(ptr), static_cast<char>(value))
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#else
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# error port atomics read/write for the current platform
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#endif
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/* clang-format on */
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//
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// The if/elif order matters here. If both OPENTELEMETRY_BUILD_IMPORT_DLL and
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// OPENTELEMETRY_BUILD_EXPORT_DLL are defined, the former takes precedence.
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//
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// TODO: consider define OPENTELEMETRY_EXPORT for cygwin/gcc, see below link.
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// https://gcc.gnu.org/wiki/Visibility#How_to_use_the_new_C.2B-.2B-_visibility_support
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//
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#if defined(_MSC_VER) && defined(OPENTELEMETRY_BUILD_IMPORT_DLL)
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# define OPENTELEMETRY_EXPORT __declspec(dllimport)
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#elif defined(_MSC_VER) && defined(OPENTELEMETRY_BUILD_EXPORT_DLL)
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# define OPENTELEMETRY_EXPORT __declspec(dllexport)
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#else
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//
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// build OpenTelemetry as static library or not on Windows.
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//
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# define OPENTELEMETRY_EXPORT
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#endif
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