[lld] [lld] lld/ELF/Writer.cpp: write directly to outs when output is "-" (PR #72061)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lld

Author: Keith Winstein (keithw)

<details>
<summary>Changes</summary>

This PR lets the LLD ELF driver write directly to outs (skipping the filesystem) when the output filename is "-".
This is a step towards being able to use LLD as a library without using an `open` syscall.

---
Full diff: https://github.com/llvm/llvm-project/pull/72061.diff


1 Files Affected:

- (modified) lld/ELF/Writer.cpp (+7) 


``````````diff
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index a84e4864ab0e5a5..b5d0c0cafd230dd 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -652,6 +652,13 @@ template <class ELFT> void Writer<ELFT>::run() {
     if (errorCount())
       return;
 
+    if (config->outputFile == "-") {
+      lld::outs() << StringRef((const char *)buffer->getBufferStart(),
+                               buffer->getBufferSize());
+      lld::outs().flush();
+      return;
+    }
+
     if (auto e = buffer->commit())
       fatal("failed to write output '" + buffer->getPath() +
             "': " + toString(std::move(e)));

``````````

</details>


https://github.com/llvm/llvm-project/pull/72061