[llvm] fix zlib buffer truncate edge cases and fix nits in tests

- add check before truncating (un)compressed data buffer if the buffer is already a perfect length, to avoid triggering truncate assertion in edge case.
- explictly coerce LLVM_ENABLE_ZLIB to a 0 or 1 value in OFF case, to match current ON, FORCE_ON behavior.
- fix code style nits in zlib tests

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D129698

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Support/Compression.cpp b/llvm/lib/Support/Compression.cpp
index 00f88a3..eda67c5 100644
--- a/llvm/lib/Support/Compression.cpp
+++ b/llvm/lib/Support/Compression.cpp
@@ -57,7 +57,8 @@ void zlib::compress(StringRef InputBuffer,
   // Tell MemorySanitizer that zlib output buffer is fully initialized.
   // This avoids a false report when running LLVM with uninstrumented ZLib.
   __msan_unpoison(CompressedBuffer.data(), CompressedSize);
-  CompressedBuffer.truncate(CompressedSize);
+  if (CompressedSize < CompressedBuffer.size())
+    CompressedBuffer.truncate(CompressedSize);
 }
 
 Error zlib::uncompress(StringRef InputBuffer, char *UncompressedBuffer,
@@ -79,7 +80,8 @@ Error zlib::uncompress(StringRef InputBuffer,
   UncompressedBuffer.resize_for_overwrite(UncompressedSize);
   Error E = zlib::uncompress(InputBuffer, UncompressedBuffer.data(),
                              UncompressedSize);
-  UncompressedBuffer.truncate(UncompressedSize);
+  if (UncompressedSize < UncompressedBuffer.size())
+    UncompressedBuffer.truncate(UncompressedSize);
   return E;
 }