tree 1381052ec05da2e9765d61717871d423a79c1707
parent ab4e181ea8a1b11546328cb71c330772b8720db7
author Andrew Rogers <andrurogerz@gmail.com> 1745340558 -0700
committer GitHub <noreply@github.com> 1745340558 -0700
gpgsig -----BEGIN PGP SIGNATURE-----
 
 wsFcBAABCAAQBQJoB8iOCRC1aQ7uu5UhlAAA/mEQACycghiRKu05GW4+i9Lrg+vx
 AT40sSxuOBarcQNroe+gJ6W/vw6l9fUYGYQlnSnyo37K9pSOgUxeGEa7mbBXQ6zk
 69ICPX2UmUb2+7BnQ/svZghZCDrCQDcbU5tJA1xEfZhvK0yT2WbPSa7GvrnY+sne
 fBgThOlTJW2Rsx3GGz3lmDD22gr7nfPoZ+xBofj+f5pHbwuAeVcyaepTr1IhGL3h
 tGGoEWQN4PVe8DizZaXx0Ky9U6RxRai1NK2L7JRjWslv3JKOrdJKkBRUxzbp9mtd
 aH83JQX36o1QIOvQk+hp/da2XhcpBJYd/U0lyK+QTgRh9kE/bDZv8WelsWYl6UbO
 6x/WjtTWJwiOVb60S0TztGKFVrvYhJfbaiONbY26+PJEu9dqcdraoy9u5ApMUu7V
 x9JrP4WnMrF4C98SgimFJQrnIhpV3rUP6rGvOr7GUGe4pVxa4OBzHwpAa/mcDVlw
 W9WHqyW3VPe+DWMW1SFUDYiuPmgw71GmwKGg4x9Nhi0RW3WJwBSuMlfiRaEBaI+H
 ZgDheTK1WuEn/dGfApub3LwqDbyIz9KCXuVZhDZWwS+nlPN37XbdsyRU71iJthMZ
 6rm9043NsCAMJ3HT0IIyDU/iUZdRG92F5qs/0w67WLo2pa3FN/R1o7evlh3ehaxm
 1M50H3j197QszqDj9PNa
 =zrAw
 -----END PGP SIGNATURE-----
 

[llvm] add LLVM_ABI_FRIEND macro for friend function decls (#136595)

## Purpose
Introduce a new `LLVM_ABI_FRIEND` macro to `llvm/Support/Compiler.h` for
annotating `friend` function declarations for DLL export.

## Overview
1. Add a new `LLVM_ABI_FRIEND` macro, which behaves identically to the
existing `LLVM_ABI` macro on Windows and compiles to nothing on other
platforms.
2. Update existing documentation to describe proper usage of the
`LLVM_ABI_FRIEND` annotation.

## Background
* MSVC issues a warning when it encounters a `friend` function
declaration that does not match the DLL import/export annotation of the
original function.
* When compiling ELF and Mach-O shared libraries, `friend` function
declarations with visibility annotations produce compilation errors
(GCC) and warnings (Clang).
* Additional context on the effort to annotate LLVM's public interface
is in [this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307).