Fix raw_fd_ostream::write_impl hang due to an infinite loop with large output

On windows when raw_fd_ostream::write_impl calls write, a 32 bit input is required for character count. As a variable with size_t is used for this argument, on x64 integral demotion occurs. In the case of large files an infinite loop follows. 
See: https://bugs.llvm.org/show_bug.cgi?id=37926
This fix allows the output of files larger than the previous int32 limit.

Differential Revision: https://reviews.llvm.org/D48948

llvm-svn: 339027

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index 038ad00bd60..1dae469958f 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -613,10 +613,10 @@ void raw_fd_ostream::write_impl(const char *Ptr, size_t Size) {
   assert(FD >= 0 && "File already closed.");
   pos += Size;
 
-  // The maximum write size is limited to SSIZE_MAX because a write
-  // greater than SSIZE_MAX is implementation-defined in POSIX.
-  // Since SSIZE_MAX is not portable, we use SIZE_MAX >> 1 instead.
-  size_t MaxWriteSize = SIZE_MAX >> 1;
+  // The maximum write size is limited to INT32_MAX. A write
+  // greater than SSIZE_MAX is implementation-defined in POSIX,
+  // and Windows _write requires 32 bit input.
+  size_t MaxWriteSize = INT32_MAX;
 
 #if defined(__linux__)
   // It is observed that Linux returns EINVAL for a very large write (>2G).