nvtx3/nvtxDetail/nvtxLinkOnce.h

0001 /*
0002  * SPDX-FileCopyrightText: Copyright (c) 2009-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
0003  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0004  *
0005  * Licensed under the Apache License, Version 2.0 (the "License");
0006  * you may not use this file except in compliance with the License.
0007  * You may obtain a copy of the License at
0008  *
0009  *     http://www.apache.org/licenses/LICENSE-2.0
0010  *
0011  * Unless required by applicable law or agreed to in writing, software
0012  * distributed under the License is distributed on an "AS IS" BASIS,
0013  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0014  * See the License for the specific language governing permissions and
0015  * limitations under the License.
0016  *
0017  * Licensed under the Apache License v2.0 with LLVM Exceptions.
0018  * See https://nvidia.github.io/NVTX/LICENSE.txt for license information.
0019  */
0020
0021 #if defined(NVTX_AS_SYSTEM_HEADER)
0022 #if defined(__clang__)
0023 #pragma clang system_header
0024 #elif defined(__GNUC__) || defined(__NVCOMPILER)
0025 #pragma GCC system_header
0026 #elif defined(_MSC_VER)
0027 #pragma system_header
0028 #endif
0029 #endif
0030
0031 #ifndef __NVTX_LINKONCE_H__
0032 #define __NVTX_LINKONCE_H__
0033
0034 /* This header defines macros to permit making definitions of global variables
0035  * and functions in C/C++ header files which may be included multiple times in
0036  * a translation unit or linkage unit.  It allows authoring header-only libraries
0037  * which can be used by multiple other header-only libraries (either as the same
0038  * copy or multiple copies), and does not require any build changes, such as
0039  * adding another .c file, linking a static library, or deploying a dynamic
0040  * library.  Globals defined with these macros have the property that they have
0041  * the same address, pointing to a single instance, for the entire linkage unit.
0042  * It is expected but not guaranteed that each linkage unit will have a separate
0043  * instance.
0044  *
0045  * In some situations it is desirable to declare a variable without initializing
0046  * it, refer to it in code or other variables' initializers, and then initialize
0047  * it later.  Similarly, functions can be prototyped, have their address taken,
0048  * and then have their body defined later.  In such cases, use the FWDDECL macros
0049  * when forward-declaring LINKONCE global variables without initializers and
0050  * function prototypes, and then use the DEFINE macros when later defining them.
0051  * Although in many cases the FWDDECL macro is equivalent to the DEFINE macro,
0052  * following this pattern makes code maximally portable.
0053  */
0054
0055 #if defined(_MSC_VER) /* MSVC */
0056     #if defined(__cplusplus)
0057         #define NVTX_LINKONCE_DEFINE_GLOBAL   extern "C" __declspec(selectany)
0058         #define NVTX_LINKONCE_DEFINE_FUNCTION extern "C" inline
0059     #else
0060         #define NVTX_LINKONCE_DEFINE_GLOBAL   __declspec(selectany)
0061         #define NVTX_LINKONCE_DEFINE_FUNCTION __inline
0062     #endif
0063     #define NVTX_LINKONCE_FWDDECL_GLOBAL      NVTX_LINKONCE_DEFINE_GLOBAL extern
0064 #elif defined(_WIN32) || defined(__CYGWIN__) /* MinGW */
0065     #if defined(__cplusplus)
0066         #define NVTX_LINKONCE_DEFINE_GLOBAL   __declspec(selectany)
0067         #define NVTX_LINKONCE_DEFINE_FUNCTION extern "C" inline
0068     #else
0069         #define NVTX_LINKONCE_DEFINE_GLOBAL   __declspec(selectany)
0070         #define NVTX_LINKONCE_DEFINE_FUNCTION
0071     #endif
0072     #define NVTX_LINKONCE_FWDDECL_GLOBAL      extern
0073 #else /* All others: Assume GCC, clang, or compatible */
0074     #define NVTX_LINKONCE_WEAK   __attribute__((weak))
0075     #define NVTX_LINKONCE_HIDDEN __attribute__((visibility("hidden")))
0076     #if defined(__cplusplus)
0077         #define NVTX_LINKONCE_DEFINE_GLOBAL   NVTX_LINKONCE_HIDDEN NVTX_LINKONCE_WEAK
0078         #define NVTX_LINKONCE_DEFINE_FUNCTION extern "C" NVTX_LINKONCE_HIDDEN inline
0079     #else
0080         #define NVTX_LINKONCE_DEFINE_GLOBAL   NVTX_LINKONCE_HIDDEN NVTX_LINKONCE_WEAK
0081         #define NVTX_LINKONCE_DEFINE_FUNCTION NVTX_LINKONCE_HIDDEN NVTX_LINKONCE_WEAK
0082     #endif
0083     #define NVTX_LINKONCE_FWDDECL_GLOBAL      NVTX_LINKONCE_DEFINE_GLOBAL extern
0084 #endif
0085
0086 #define NVTX_LINKONCE_FWDDECL_FUNCTION        NVTX_LINKONCE_DEFINE_FUNCTION
0087
0088 #endif /* __NVTX_LINKONCE_H__ */