[llvm] DLLExport Twine (PR #127853)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Andrew Rogers (andrurogerz)

<details>
<summary>Changes</summary>

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

---
Full diff: https://github.com/llvm/llvm-project/pull/127853.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/Twine.h (+2-1) 


``````````diff
diff --git a/llvm/include/llvm/ADT/Twine.h b/llvm/include/llvm/ADT/Twine.h
index 1f1fd1967efbc..e50916f6d003f 100644
--- a/llvm/include/llvm/ADT/Twine.h
+++ b/llvm/include/llvm/ADT/Twine.h
@@ -11,6 +11,7 @@
 
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <cassert>
 #include <cstdint>
@@ -78,7 +79,7 @@ namespace llvm {
   /// so we provide two additional methods (and accompanying operator+
   /// overloads) to guarantee that particularly important cases (cstring plus
   /// StringRef) codegen as desired.
-  class Twine {
+  class LLVM_ABI Twine {
     /// NodeKind - Represent the type of an argument.
     enum NodeKind : unsigned char {
       /// An empty string; the result of concatenating anything with it is also

``````````

</details>


https://github.com/llvm/llvm-project/pull/127853