SourceLevelDebugPkg: Replace include guards with #pragma once

Replace traditional `#ifndef`/`#define`/`#endif` include guards with
`#pragma` once.

`#pragma once` is a widely supported preprocessor directive that
prevents header files from being included multiple times. It is
supported by all toolchains used to build edk2: GCC, Clang/LLVM, and
MSVC.

Compared to macro-based include guards, `#pragma once`:

- Eliminates the risk of macro name collisions or copy/paste errors
  where two headers inadvertently use the same guard macro.
- Eliminate inconsistency in the way include guard macros are named
  (e.g., some files use `__FILE_H__`, others use `FILE_H_`, etc.).
- Reduces boilerplate (three lines replaced by one).
- Avoids polluting the macro namespace with guard symbols.
- Can improve build times as the preprocessor can skip re-opening the
  file entirely, rather than re-reading it to find the matching
  `#endif` ("multiple-include optimization").
  - Note that some compilers may already optimize traditional include
    guards, by recognzining the idiomatic pattern.

This change is made acknowledging that overall portability of the
code will technically be reduced, as `#pragma once` is not part of the
C/C++ standards.

However, this is considered acceptable given:

1. edk2 already defines a subset of supported compilers in
   BaseTools/Conf/tools_def.template, all of which have supported
   `#pragma once` for over two decades.
2. There have been concerns raised to the project about inconsistent
   include guard naming and potential macro collisions.

Approximate compiler support dates:

- MSVC: Supported since Visual C++ 4.2 (1996)
- GCC: Supported since 3.4 (2004)
  (http://gnu.ist.utl.pt/software/gcc/gcc-3.4/changes.html)
- Clang (LLVM based): Since initial release in 2007

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>

SourceLevelDebugPkg/Include/Guid/DebugAgentGuid.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef __EFI_DEBUG_AGENT_GUID_H__
-#define __EFI_DEBUG_AGENT_GUID_H__
+#pragma once
 
 ///
 /// This guid is used as a variable GUID for the capsule variable
@@ -22,5 +21,3 @@
   }
 
 extern EFI_GUID  gEfiDebugAgentGuid;
-
-#endif

SourceLevelDebugPkg/Include/Ia32/ProcessorContext.h

@@ -7,8 +7,7 @@
 
 **/
 
-#ifndef __PROCESSOR_CONTEXT_H__
-#define __PROCESSOR_CONTEXT_H__
+#pragma once
 
 //
 //  IA-32/x64 processor register index table
@@ -299,5 +298,3 @@ typedef struct {
 } DEBUG_DATA_X64_SYSTEM_CONTEXT;
 
 #pragma pack()
-
-#endif

SourceLevelDebugPkg/Include/ImageDebugSupport.h

@@ -7,8 +7,7 @@
 
 **/
 
-#ifndef __IMAGE_DEBUG_SUPPORT_H__
-#define __IMAGE_DEBUG_SUPPORT_H__
+#pragma once
 
 #define IO_PORT_BREAKPOINT_ADDRESS  0x84
 #define IMAGE_LOAD_SIGNATURE        SIGNATURE_32('L','O','A','D')
@@ -17,5 +16,3 @@
 
 #define DEBUG_AGENT_IMAGE_WAIT      0x00
 #define DEBUG_AGENT_IMAGE_CONTINUE  0x01
-
-#endif

SourceLevelDebugPkg/Include/Library/DebugCommunicationLib.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef __DEBUG_COMMUNICATION_LIB_H__
-#define __DEBUG_COMMUNICATION_LIB_H__
+#pragma once
 
 typedef VOID *DEBUG_PORT_HANDLE;
 
@@ -139,5 +138,3 @@ EFIAPI
 DebugPortPollBuffer (
   IN DEBUG_PORT_HANDLE  Handle
   );
-
-#endif

SourceLevelDebugPkg/Include/TransferProtocol.h

@@ -7,8 +7,7 @@
 
 **/
 
-#ifndef __TRANSFER_PROTOCOL_H__
-#define __TRANSFER_PROTOCOL_H__
+#pragma once
 
 #include "ProcessorContext.h"
 
@@ -365,5 +364,3 @@ typedef struct {
 } DEBUG_DATA_RESPONSE_SEARCH_SIGNATURE;
 
 #pragma pack()
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DEBUG_AGENT_H_
-#define _DEBUG_AGENT_H_
+#pragma once
 
 #include <Register/LocalApic.h>
 #include <Guid/DebugAgentGuid.h>
@@ -492,5 +491,3 @@ DebugAgentReadBuffer (
   IN     UINTN              NumberOfBytes,
   IN     UINTN              Timeout
   );
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugMp.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DEBUG_MP_H_
-#define _DEBUG_MP_H_
+#pragma once
 
 #define DEBUG_CPU_MAX_COUNT  256
 
@@ -211,5 +210,3 @@ BOOLEAN
 IsFirstBreakProcessor (
   IN UINT32  ProcessorIndex
   );
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DEBUG_TIMER_H_
-#define _DEBUG_TIMER_H_
+#pragma once
 
 /**
   Initialize CPU local APIC timer.
@@ -40,5 +39,3 @@ IsDebugTimerTimeout (
   IN UINT32  Timer,
   IN UINT32  TimeoutTicker
   );
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Ia32/ArchDebugSupport.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _ARCH_DEBUG_SUPPORT_H_
-#define _ARCH_DEBUG_SUPPORT_H_
+#pragma once
 
 #include "ProcessorContext.h"
 #include "TransferProtocol.h"
@@ -17,5 +16,3 @@
 
 typedef DEBUG_DATA_IA32_FX_SAVE_STATE   DEBUG_DATA_FX_SAVE_STATE;
 typedef DEBUG_DATA_IA32_SYSTEM_CONTEXT  DEBUG_CPU_CONTEXT;
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/Ia32/DebugException.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DEBUG_EXCEPTION_H_
-#define _DEBUG_EXCEPTION_H_
+#pragma once
 
 #define DEBUG_EXCEPT_DIVIDE_ERROR     0
 #define DEBUG_EXCEPT_DEBUG            1
@@ -26,5 +25,3 @@
 #define DEBUG_EXCEPT_ALIGNMENT_CHECK  17
 #define DEBUG_EXCEPT_MACHINE_CHECK    18
 #define DEBUG_EXCEPT_SIMD             19
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/X64/ArchDebugSupport.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _ARCH_DEBUG_SUPPORT_H_
-#define _ARCH_DEBUG_SUPPORT_H_
+#pragma once
 
 #include "ProcessorContext.h"
 #include "TransferProtocol.h"
@@ -17,5 +16,3 @@
 
 typedef DEBUG_DATA_X64_FX_SAVE_STATE   DEBUG_DATA_FX_SAVE_STATE;
 typedef DEBUG_DATA_X64_SYSTEM_CONTEXT  DEBUG_CPU_CONTEXT;
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/X64/DebugException.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DEBUG_EXCEPTION_H_
-#define _DEBUG_EXCEPTION_H_
+#pragma once
 
 #define DEBUG_EXCEPT_DIVIDE_ERROR     0
 #define DEBUG_EXCEPT_DEBUG            1
@@ -26,5 +25,3 @@
 #define DEBUG_EXCEPT_ALIGNMENT_CHECK  17
 #define DEBUG_EXCEPT_MACHINE_CHECK    18
 #define DEBUG_EXCEPT_SIMD             19
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/DxeDebugAgent/DxeDebugAgentLib.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _DXE_CORE_DEBUG_AGENT_LIB_H_
-#define _DXE_CORE_DEBUG_AGENT_LIB_H_
+#pragma once
 
 #include <PiDxe.h>
 
@@ -30,5 +29,3 @@ VOID
 InstallSerialIo (
   VOID
   );
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/SecPeiDebugAgent/SecPeiDebugAgentLib.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _SEC_CORE_DEBUG_AGENT_LIB_H_
-#define _SEC_CORE_DEBUG_AGENT_LIB_H_
+#pragma once
 
 #include <PiPei.h>
 #include <Ppi/MemoryDiscovered.h>
@@ -54,5 +53,3 @@ DebugAgentCallbackMemoryDiscoveredPpi (
   IN EFI_PEI_NOTIFY_DESCRIPTOR  *NotifyDescriptor,
   IN VOID                       *Ppi
   );
-
-#endif

SourceLevelDebugPkg/Library/DebugAgent/SmmDebugAgent/SmmDebugAgentLib.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _SMM_DEBUG_AGENT_LIB_H_
-#define _SMM_DEBUG_AGENT_LIB_H_
+#pragma once
 
 #include <PiDxe.h>
 
@@ -15,5 +14,3 @@
 #include <Library/SmmServicesTableLib.h>
 
 #include "DebugAgent.h"
-
-#endif

SourceLevelDebugPkg/Library/DebugCommunicationLibUsb3/DebugCommunicationLibUsb3Internal.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef __USB3_DEBUG_PORT_LIB_INTERNAL__
-#define __USB3_DEBUG_PORT_LIB_INTERNAL__
+#pragma once
 
 #include <Uefi.h>
 #include <Base.h>
@@ -733,5 +732,3 @@ USB3_DEBUG_PORT_HANDLE *
 GetUsb3DebugPortInstance (
   VOID
   );
-
-#endif //__SERIAL_PORT_LIB_USB__

SourceLevelDebugPkg/Library/PeCoffExtraActionLibDebug/PeCoffExtraActionLib.h

@@ -6,8 +6,7 @@
 
 **/
 
-#ifndef _PE_COFF_EXTRA_ACTION_LIB_H_
-#define _PE_COFF_EXTRA_ACTION_LIB_H_
+#pragma once
 
 #include <Base.h>
 #include <Library/PeCoffExtraActionLib.h>
@@ -68,5 +67,3 @@ RestoreIdtEntry1 (
   IN  IA32_DESCRIPTOR           *IdtDescriptor,
   IN  IA32_IDT_GATE_DESCRIPTOR  *RestoredIdtEntry
   );
-
-#endif