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RFC: [llvm] refactor common export macros to llvm/Config #149175

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RFC: [llvm] refactor common export macros to llvm/Config #149175

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3 changes: 3 additions & 0 deletions llvm/CMakeLists.txt
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Expand Up @@ -1228,6 +1228,9 @@ endif()
configure_file(
${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/config.h.cmake
${LLVM_INCLUDE_DIR}/llvm/Config/config.h)
configure_file(
${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/export-config.h.cmake
${LLVM_INCLUDE_DIR}/llvm/Config/export-config.h)
configure_file(
${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/llvm-config.h.cmake
${LLVM_INCLUDE_DIR}/llvm/Config/llvm-config.h)
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20 changes: 3 additions & 17 deletions llvm/include/llvm-c/Visibility.h
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Expand Up @@ -16,29 +16,15 @@
#ifndef LLVM_C_VISIBILITY_H
#define LLVM_C_VISIBILITY_H

#include "llvm/Config/llvm-config.h"
#include "llvm/Config/export-config.h"

/// LLVM_C_ABI is the export/visibility macro used to mark symbols declared in
/// llvm-c as exported when built as a shared library.

#if !defined(LLVM_ABI_GENERATING_ANNOTATIONS)
// TODO(https://github.com/llvm/llvm-project/issues/145406): eliminate need for
// two preprocessor definitions to gate LLVM_ABI macro definitions.
#if defined(LLVM_ENABLE_LLVM_C_EXPORT_ANNOTATIONS) && \
!defined(LLVM_BUILD_STATIC)
#if defined(_WIN32) && !defined(__MINGW32__)
#if defined(LLVM_EXPORTS)
#define LLVM_C_ABI __declspec(dllexport)
#if defined(LLVM_ENABLE_LLVM_C_EXPORT_ANNOTATIONS)
#define LLVM_C_ABI LLVM_INTERFACE_ABI
#else
#define LLVM_C_ABI __declspec(dllimport)
#endif
#elif defined(__has_attribute) && __has_attribute(visibility)
#define LLVM_C_ABI __attribute__((visibility("default")))
#endif
#endif
#if !defined(LLVM_C_ABI)
#define LLVM_C_ABI
#endif
#endif

#endif
88 changes: 88 additions & 0 deletions llvm/include/llvm/Config/export-config.h.cmake
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@@ -0,0 +1,88 @@
/*===------- llvm/Config/export-config.h - export configuration ----- 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 file contains configuration definitions controling which LLVM projects
and components require public ABI export for shared library builds. It also
contains generic LLVM_INTERFACE_ macro definitions that can be aliased by
libraries and components and used to decorate their public interface. */

#ifndef LLVM_EXPORT_CONFIG_H
#define LLVM_EXPORT_CONFIG_H

/* Define if exporting LLVM public interface for shared library */
#cmakedefine LLVM_ENABLE_LLVM_EXPORT_ANNOTATIONS

/* Define if exporting LLVM-C public interface for shared library */
#cmakedefine LLVM_ENABLE_LLVM_C_EXPORT_ANNOTATIONS

/// LLVM_INTERFACE_ABI is the main export/visibility macro to mark something as explicitly
/// exported when llvm is built as a shared library with everything else that is
/// unannotated will have internal visibility.
///
/// LLVM_INTERFACE_ABI_EXPORT is for the special case for things like plugin symbol
/// declarations or definitions where we don't want the macro to be switching
/// between dllexport and dllimport on windows based on what codebase is being
/// built, it will only be dllexport. For non windows platforms this macro
/// behaves the same as LLVM_ABI.
///
/// LLVM_INTERFACE_EXPORT_TEMPLATE is used on explicit template instantiations in source
/// files that were declared extern in a header. This macro is only set as a
/// compiler export attribute on windows, on other platforms it does nothing.
///
/// LLVM_INTERFACE_TEMPLATE_ABI is for annotating extern template declarations in headers
/// for both functions and classes. On windows its turned in to dllimport for
/// library consumers, for other platforms its a default visibility attribute.
///
/// LLVM_INTERFACE_ABI_FOR_TEST is for annotating symbols that are only exported because
/// they are imported from a test. These symbols are not technically part of the
/// LLVM public interface and could be conditionally excluded when not building
/// tests in the future.
///
// Marker to add to classes or functions in public headers that should not have
// export macros added to them by the clang tool
#define LLVM_INTERFACE_ABI_NOT_EXPORTED
// TODO(https://github.com/llvm/llvm-project/issues/145406): eliminate need for
// two preprocessor definitions to gate LLVM_ABI macro definitions.
#if !defined(LLVM_BUILD_STATIC)
#if defined(_WIN32) && !defined(__MINGW32__)
#if defined(LLVM_EXPORTS)
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@compnerd compnerd Jul 16, 2025 •
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This doesn't work. This defines the interface as to how LLVM was built. If I build LLVM dynamically, llvm-c statically, and LLVM Demangle dynamically, I need 2 independent sets of definitions for LLVM and LLVM Demangle. Doing something else really doesn't work. The de-duplication is not worth additional complexity and introducing new patterns IMO.

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@andrurogerz andrurogerz Jul 16, 2025

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The de-duplication is not worth additional complexity and introducing new patterns IMO.

I am completely on-board with the complexity argument for not doing it this way. I will put up the abi-breaking PR again with the duplicated logic.

#define LLVM_INTERFACE_ABI __declspec(dllexport)
#define LLVM_INTERFACE_TEMPLATE_ABI
#define LLVM_INTERFACE_EXPORT_TEMPLATE __declspec(dllexport)
#else
#define LLVM_INTERFACE_ABI __declspec(dllimport)
#define LLVM_INTERFACE_TEMPLATE_ABI __declspec(dllimport)
#define LLVM_INTERFACE_EXPORT_TEMPLATE
#endif
#define LLVM_INTERFACE_ABI_EXPORT __declspec(dllexport)
#elif defined(__has_attribute) && __has_attribute(visibility)
#if defined(__ELF__) || defined(__MINGW32__) || defined(_AIX) || \
defined(__MVS__) || defined(__CYGWIN__)
#define LLVM_INTERFACE_ABI __attribute__((visibility("default")))
#define LLVM_INTERFACE_TEMPLATE_ABI LLVM_INTERFACE_ABI
#define LLVM_INTERFACE_EXPORT_TEMPLATE
#define LLVM_INTERFACE_ABI_EXPORT LLVM_INTERFACE_ABI
#elif defined(__MACH__) || defined(__WASM__) || defined(__EMSCRIPTEN__)
#define LLVM_INTERFACE_ABI __attribute__((visibility("default")))
#define LLVM_INTERFACE_TEMPLATE_ABI
#define LLVM_INTERFACE_EXPORT_TEMPLATE
#define LLVM_INTERFACE_ABI_EXPORT LLVM_INTERFACE_ABI
#endif
#endif
#endif
#if !defined(LLVM_INTERFACE_ABI)
#define LLVM_INTERFACE_ABI
#define LLVM_INTERFACE_TEMPLATE_ABI
#define LLVM_INTERFACE_EXPORT_TEMPLATE
#define LLVM_INTERFACE_ABI_EXPORT
#endif
#define LLVM_INTERFACE_ABI_FOR_TEST LLVM_INTERFACE_ABI

#endif
6 changes: 0 additions & 6 deletions llvm/include/llvm/Config/llvm-config.h.cmake
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Expand Up @@ -110,12 +110,6 @@
/* Define if building LLVM with BUILD_SHARED_LIBS */
#cmakedefine LLVM_BUILD_SHARED_LIBS

/* Define if exporting LLVM public interface for shared library */
#cmakedefine LLVM_ENABLE_LLVM_EXPORT_ANNOTATIONS

/* Define if exporting LLVM-C public interface for shared library */
#cmakedefine LLVM_ENABLE_LLVM_C_EXPORT_ANNOTATIONS

/* Define if building LLVM with LLVM_FORCE_USE_OLD_TOOLCHAIN_LIBS */
#cmakedefine LLVM_FORCE_USE_OLD_TOOLCHAIN ${LLVM_FORCE_USE_OLD_TOOLCHAIN}

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45 changes: 10 additions & 35 deletions llvm/include/llvm/Support/Compiler.h
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Expand Up @@ -15,6 +15,7 @@
#ifndef LLVM_SUPPORT_COMPILER_H
#define LLVM_SUPPORT_COMPILER_H

#include "llvm/Config/export-config.h"
#include "llvm/Config/llvm-config.h"

#include <stddef.h>
Expand Down Expand Up @@ -176,46 +177,20 @@
/// LLVM public interface and could be conditionally excluded when not building
/// tests in the future.
///
#ifndef LLVM_ABI_GENERATING_ANNOTATIONS
// Marker to add to classes or functions in public headers that should not have
// export macros added to them by the clang tool
#define LLVM_ABI_NOT_EXPORTED
// TODO(https://github.com/llvm/llvm-project/issues/145406): eliminate need for
// two preprocessor definitions to gate LLVM_ABI macro definitions.
#if defined(LLVM_ENABLE_LLVM_EXPORT_ANNOTATIONS) && !defined(LLVM_BUILD_STATIC)
#if defined(_WIN32) && !defined(__MINGW32__)
#if defined(LLVM_EXPORTS)
#define LLVM_ABI __declspec(dllexport)
#define LLVM_TEMPLATE_ABI
#define LLVM_EXPORT_TEMPLATE __declspec(dllexport)
#if defined(LLVM_ENABLE_LLVM_EXPORT_ANNOTATIONS)
#define LLVM_ABI_NOT_EXPORTED LLVM_INTERFACE_ABI_NOT_EXPORTED
#define LLVM_ABI LLVM_INTERFACE_ABI
#define LLVM_TEMPLATE_ABI LLVM_INTERFACE_TEMPLATE_ABI
#define LLVM_EXPORT_TEMPLATE LLVM_INTERFACE_EXPORT_TEMPLATE
#define LLVM_ABI_EXPORT LLVM_INTERFACE_ABI_EXPORT
#define LLVM_ABI_FOR_TEST LLVM_INTERFACE_ABI_FOR_TEST
#else
#define LLVM_ABI __declspec(dllimport)
#define LLVM_TEMPLATE_ABI __declspec(dllimport)
#define LLVM_EXPORT_TEMPLATE
#endif
#define LLVM_ABI_EXPORT __declspec(dllexport)
#elif __has_attribute(visibility)
#if defined(__ELF__) || defined(__MINGW32__) || defined(_AIX) || \
defined(__MVS__) || defined(__CYGWIN__)
#define LLVM_ABI __attribute__((visibility("default")))
#define LLVM_TEMPLATE_ABI LLVM_ABI
#define LLVM_EXPORT_TEMPLATE
#define LLVM_ABI_EXPORT LLVM_ABI
#elif defined(__MACH__) || defined(__WASM__) || defined(__EMSCRIPTEN__)
#define LLVM_ABI __attribute__((visibility("default")))
#define LLVM_TEMPLATE_ABI
#define LLVM_EXPORT_TEMPLATE
#define LLVM_ABI_EXPORT LLVM_ABI
#endif
#endif
#endif
#if !defined(LLVM_ABI)
#define LLVM_ABI_NOT_EXPORTED
#define LLVM_ABI
#define LLVM_TEMPLATE_ABI
#define LLVM_EXPORT_TEMPLATE
#define LLVM_ABI_EXPORT
#endif
#define LLVM_ABI_FOR_TEST LLVM_ABI
#define LLVM_ABI_FOR_TEST
#endif

#if defined(__GNUC__)
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