[llvm] [llvm] DLLExport BinaryStreamError (PR #127909)

[Andrew Rogers via llvm-commits]

https://github.com/andrurogerz created https://github.com/llvm/llvm-project/pull/127909

## Overview
Annotate the `llvm::BinaryStreamError` class so it is explicitly included in LLVM's public interface. When building LLVM as a Windows DLL, this annotation exports `BinaryStreamError`'s public methods from the DLL.

## Background
This change is required as part of the overall project to build LLVM as a Windows DLL described in #109483. Without this change, LLVM tools fail to link.

## Validation
Built LLVM with MSVC on Windows 11:
```
cmake -B build -S llvm -G Ninja -DCMAKE_BUILD_TYPE=Debug -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_OPTIMIZED_TABLEGEN -DLLVM_BUILD_LLVM_DYLIB=ON -DLLVM_BUILD_LLVM_DYLIB_VIS=ON -DLLVM_LINK_LLVM_DYLIB=ON -DCLANG_LINK_CLANG_DYLIB=ON
ninja -C build llvm-rc llvm-ar
```
Verified the annotated interface no longer appears in the list of unresolved external symbols.

>From 2d468320d1580db487e27d473bd9db735e7c39cb Mon Sep 17 00:00:00 2001
From: Andrew Rogers <andrurogerz at gmail.com>
Date: Wed, 19 Feb 2025 12:34:03 -0800
Subject: [PATCH] DLLExport BinaryStreamError

---
 llvm/include/llvm/Support/BinaryStreamError.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/include/llvm/Support/BinaryStreamError.h b/llvm/include/llvm/Support/BinaryStreamError.h
index cf6e034ffd2ce..8a45f7bbd52cc 100644
--- a/llvm/include/llvm/Support/BinaryStreamError.h
+++ b/llvm/include/llvm/Support/BinaryStreamError.h
@@ -10,6 +10,7 @@
 #define LLVM_SUPPORT_BINARYSTREAMERROR_H
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Error.h"
 
 #include <string>
@@ -24,7 +25,7 @@ enum class stream_error_code {
 };
 
 /// Base class for errors originating when parsing raw PDB files
-class BinaryStreamError : public ErrorInfo<BinaryStreamError> {
+class LLVM_ABI BinaryStreamError : public ErrorInfo<BinaryStreamError> {
 public:
   static char ID;
   explicit BinaryStreamError(stream_error_code C);