Use posix_fallocate instead of ftruncate.

This makes sure that space is actually available. With this change
running lld on a full file system causes it to exit with

failed to open foo: No space left on device

instead of crashing with a sigbus.

llvm-svn: 276017

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 84aafcb..ea439c6 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -329,8 +329,17 @@ std::error_code rename(const Twine &from, const Twine &to) {
 }
 
 std::error_code resize_file(int FD, uint64_t Size) {
+#if defined(HAVE_POSIX_FALLOCATE)
+  // If we have posix_fallocate use it. Unlike ftruncate it always allocates
+  // space, so we get an error if the disk is full.
+  if (int Err = ::posix_fallocate(FD, 0, Size))
+    return std::error_code(Err, std::generic_category());
+#else
+  // Use ftruncate as a fallback. It may or may not allocate space. At least on
+  // OS X with HFS+ it does.
   if (::ftruncate(FD, Size) == -1)
     return std::error_code(errno, std::generic_category());
+#endif
 
   return std::error_code();
 }