Modernize: Use #pragma once in all header files

#pragma once is a widely supported compiler pragma, even though it is
not part of the C++ standard. Many of the issues keeping #pragma once
from being standardized (distributed filesystems, build farms, hard
links, etc.) do not apply to CMake - it is easy to build CMake on a
single machine. CMake also does not install any header files which can
be consumed by other projects (though cmCPluginAPI.h has been
deliberately omitted from this conversion in case anyone is still using
it.) Finally, #pragma once has been required to build CMake since at
least August 2017 (7f29bbe6 enabled server mode unconditionally, which
had been using #pragma once since September 2016 (b13d3e0d)). The fact
that we now require C++11 filters out old compilers, and it is unlikely
that there is a compiler which supports C++11 but does not support
#pragma once.

1 files changed, 1 insertions, 4 deletions

diff --git a/Utilities/std/cm/shared_mutex b/Utilities/std/cm/shared_mutex
index ec63a7b..a1204fa 100644
--- a/Utilities/std/cm/shared_mutex
+++ b/Utilities/std/cm/shared_mutex
@@ -3,8 +3,7 @@
 
 /* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
    file Copyright.txt or https://cmake.org/licensing for details.  */
-#ifndef cm_shared_mutex
-#define cm_shared_mutex
+#pragma once
 
 #if __cplusplus >= 201402L || defined(_MSVC_LANG) && _MSVC_LANG >= 201402L
 #  define CMake_HAVE_CXX_SHARED_LOCK
@@ -72,5 +71,3 @@ public:
 };
 #endif
 }
-
-#endif