[libcxxabi] [llvm] [llvm] annotate interfaces in Demangle for DLL export (PR #147564)

[Andrew Rogers via llvm-commits]

================
@@ -0,0 +1,43 @@
+/*===-- Demangle/Visibility.h - Visibility macros for Demangle --*- C++ -*-===*\
+|*                                                                            *|
+|* Part of the LLVM Project, under the Apache License v2.0 with LLVM          *|
+|* Exceptions.                                                                *|
+|* See https://llvm.org/LICENSE.txt for license information.                  *|
+|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception                    *|
+|*                                                                            *|
+|*===----------------------------------------------------------------------===*|
+|*                                                                            *|
+|* This header defines visibility macros used for the Demangle library. These *|
+|* macros are used to annotate functions that should be exported as part of a *|
+|* shared library or DLL.                                                     *|
+|*                                                                            *|
+\*===----------------------------------------------------------------------===*/
+
+#ifndef LLVM_DEMANGLE_VISIBILITY_H
+#define LLVM_DEMANGLE_VISIBILITY_H
+
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Demangle/DemangleConfig.h"
+
+/// DEMANGLE_ABI is the export/visibility macro used to mark symbols delcared in
+/// llvm/Demangle as exported when built as a shared library.
+
+#if !defined(LLVM_ABI_GENERATING_ANNOTATIONS)
+#if defined(LLVM_ENABLE_DEMANGLE_EXPORT_ANNOTATIONS) &&                        \
+    !defined(LLVM_BUILD_STATIC)
+#if defined(_WIN32) && !defined(__MINGW32__)
+#if defined(LLVM_EXPORTS)
+#define DEMANGLE_ABI __declspec(dllexport)
+#else
+#define DEMANGLE_ABI __declspec(dllimport)
+#endif
+#elif __has_attribute(visibility)
+#define DEMANGLE_ABI __attribute__((visibility("default")))
+#endif
+#endif
+#if !defined(DEMANGLE_ABI)
+#define DEMANGLE_ABI
+#endif
+#endif
----------------
andrurogerz wrote:

@nikic it would be simpler if OK. But if that's safe, can I just use `LLVM_ABI` instead of a new `DEMANGLE_ABI` and no-op `LLVM_ABI` in `libcxxabi/src/demangle/DemangleConfig.h` for the `libcxxabi` copy? That would be even simpler.

https://github.com/llvm/llvm-project/pull/147564