Use std::error_code instead of llvm::error_code.

The idea of this patch is to turn llvm/Support/system_error.h into a
transitional header that just brings in the erorr_code api to the llvm
namespace. I will remove it shortly afterwards.

The cases where the general idea needed some tweaking:

* std::errc is a namespace in msvc, so we cannot use "using std::errc". I could
add an #ifdef, but there were not that many uses, so I just added std:: to
them in this patch.

* Template specialization had to be moved to the std namespace in this
patch set already.

* The msvc implementation of default_error_condition doesn't seem to
provide the same transformations as we need. Not too surprising since
the standard doesn't actually say what "equivalent" means. I fixed the
problem by keeping our old mapping and using it at error_code
construction time.

Despite these shortcomings I think this is still a good thing. Some reasons:

* The different implementations of system_error might improve over time.
* It removes 925 lines of code from llvm already.
* It removes 6313 bytes from the text segment of the clang binary when
it is built with gcc and 2816 bytes when building with clang and
libstdc++.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210687 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 2 deletions

diff --git a/include/llvm/Support/FileOutputBuffer.h b/include/llvm/Support/FileOutputBuffer.h
index a8a48fa3fe..40a883ab3b 100644
--- a/include/llvm/Support/FileOutputBuffer.h
+++ b/include/llvm/Support/FileOutputBuffer.h
@@ -20,8 +20,6 @@
 #include "llvm/Support/FileSystem.h"
 
 namespace llvm {
-class error_code;
-
 /// FileOutputBuffer - This interface provides simple way to create an in-memory
 /// buffer which will be written to a file. During the lifetime of these
 /// objects, the content or existence of the specified file is undefined. That