[PATCH] D48948: Fix raw_fd_ostream::write_impl hang due to an infinite loop with large output

[Owen Reynolds via Phabricator via llvm-commits]

gbreynoo created this revision.
gbreynoo added reviewers: zturner, pcc.
Herald added a subscriber: llvm-commits.

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 previous int32 limit.


Repository:
  rL LLVM

https://reviews.llvm.org/D48948

Files:
  lib/Support/raw_ostream.cpp


Index: lib/Support/raw_ostream.cpp
===================================================================
--- lib/Support/raw_ostream.cpp
+++ lib/Support/raw_ostream.cpp
@@ -613,10 +613,15 @@
   assert(FD >= 0 && "File already closed.");
   pos += Size;
 
+#ifdef _WIN64
+  // Windows write() requires signed 32 bit input so SIZE_MAX can not be used 
+  size_t MaxWriteSize = _I32_MAX;
+#else
   // 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;
+#endif
 
 #if defined(__linux__)
   // It is observed that Linux returns EINVAL for a very large write (>2G).


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