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++.

llvm-svn: 210687

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/tools/llvm-readobj/Error.h b/llvm/tools/llvm-readobj/Error.h
index ebf652e9a18..b3aab327cbe 100644
--- a/llvm/tools/llvm-readobj/Error.h
+++ b/llvm/tools/llvm-readobj/Error.h
@@ -33,8 +33,10 @@ inline error_code make_error_code(readobj_error e) {
   return error_code(static_cast<int>(e), readobj_category());
 }
 
-template <> struct is_error_code_enum<readobj_error> : std::true_type { };
-
 } // namespace llvm
 
+namespace std {
+template <> struct is_error_code_enum<llvm::readobj_error> : std::true_type {};
+}
+
 #endif