[edk2-devel] [PATCH V6] DebugLib: Update DEBUG macro used when MDEPKG_NDEBUG is defined

["Mike Beaton" <mjsbeaton@gmail.com>]

From: Mike Beaton <mjsbeaton@gmail.com>

The variant provided when MDEPKG_NDEBUG is defined will be optimised
away in RELEASE builds, but by referencing the argument list, avoids
unused variable errors from valid debug code, for example when STATIC
variables are used only in DEBUG statements.

This issue was being caused by variable EventNames in
OvmfPkg/VirtioSerialDxe/VirtioSerial.c in CLANGPDB X64 RELEASE build
prior to this commit, and was also being caused by the same variable
in CLANGDWARF X64 RELEASE build, prior to
d3225577123767fd09c91201d27e9c91663ae132 - which we
revert, restoring the desirable feature of failure to build on
genuinely (unintentionally) unused variables when building in either
clang toolchain.

Also change manual exclusion of debug vars when MDEPKG_NDEBUG is
not defined in a similar cases in ArmPkg, to inclusion when used
regardless of MDEPKG_NDEBUG (the revised DEBUG macro automatically
compiles away unused variable accesses, but there has to be a
variable, access to which to discard).

Signed-off-by: Mike Beaton <mjsbeaton@gmail.com>
---
 .../DebugPeCoffExtraActionLib/DebugPeCoffExtraActionLib.c  | 4 ++--
 .../AArch64/DefaultExceptionHandler.c                      | 3 ---
 BaseTools/Conf/tools_def.template                          | 2 +-
 MdePkg/Include/Library/DebugLib.h                          | 7 ++++++-
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/ArmPkg/Library/DebugPeCoffExtraActionLib/DebugPeCoffExtraActionLib.c b/ArmPkg/Library/DebugPeCoffExtraActionLib/DebugPeCoffExtraActionLib.c
index 432112354f..c5c53ef3e1 100644
--- a/ArmPkg/Library/DebugPeCoffExtraActionLib/DebugPeCoffExtraActionLib.c
+++ b/ArmPkg/Library/DebugPeCoffExtraActionLib/DebugPeCoffExtraActionLib.c
@@ -71,7 +71,7 @@ PeCoffLoaderRelocateImageExtraAction (
   IN OUT PE_COFF_LOADER_IMAGE_CONTEXT  *ImageContext
   )
 {
- #if !defined (MDEPKG_NDEBUG)
+ #if defined (__CC_ARM) || defined (__GNUC__)
   CHAR8  Temp[512];
  #endif
 
@@ -106,7 +106,7 @@ PeCoffLoaderUnloadImageExtraAction (
   IN OUT PE_COFF_LOADER_IMAGE_CONTEXT  *ImageContext
   )
 {
- #if !defined (MDEPKG_NDEBUG)
+ #if defined (__CC_ARM) || defined (__GNUC__)
   CHAR8  Temp[512];
  #endif
 
diff --git a/ArmPkg/Library/DefaultExceptionHandlerLib/AArch64/DefaultExceptionHandler.c b/ArmPkg/Library/DefaultExceptionHandlerLib/AArch64/DefaultExceptionHandler.c
index a39896d576..1d3ea61311 100644
--- a/ArmPkg/Library/DefaultExceptionHandlerLib/AArch64/DefaultExceptionHandler.c
+++ b/ArmPkg/Library/DefaultExceptionHandlerLib/AArch64/DefaultExceptionHandler.c
@@ -157,7 +157,6 @@ DescribeExceptionSyndrome (
   DEBUG ((DEBUG_ERROR, "\n %a \n", Message));
 }
 
-#ifndef MDEPKG_NDEBUG
 STATIC
 CONST CHAR8 *
 BaseName (
@@ -177,8 +176,6 @@ BaseName (
   return Str;
 }
 
-#endif
-
 /**
   This is the default action to take on an unexpected exception
 
diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index c34ecfd557..eaccf0b698 100755
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -1859,7 +1859,7 @@ DEFINE CLANGDWARF_X64_DLINK2_FLAGS        = -Wl,--defsym=PECOFF_HEADER_SIZE=0x22
 DEFINE CLANGDWARF_IA32_TARGET             = -target i686-pc-linux-gnu
 DEFINE CLANGDWARF_X64_TARGET              = -target x86_64-pc-linux-gnu
 
-DEFINE CLANGDWARF_WARNING_OVERRIDES    = -Wno-parentheses-equality -Wno-empty-body -Wno-unused-const-variable -Wno-varargs -Wno-unknown-warning-option -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-unaligned-access -Wno-unneeded-internal-declaration
+DEFINE CLANGDWARF_WARNING_OVERRIDES    = -Wno-parentheses-equality -Wno-empty-body -Wno-unused-const-variable -Wno-varargs -Wno-unknown-warning-option -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-unaligned-access
 DEFINE CLANGDWARF_ALL_CC_FLAGS         = DEF(GCC48_ALL_CC_FLAGS) DEF(CLANGDWARF_WARNING_OVERRIDES) -fno-stack-protector -mms-bitfields -Wno-address -Wno-shift-negative-value -Wno-unknown-pragmas -Wno-incompatible-library-redeclaration -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -msoft-float -mno-implicit-float  -ftrap-function=undefined_behavior_has_been_optimized_away_by_clang -funsigned-char -fno-ms-extensions -Wno-null-dereference
 
 ###########################
diff --git a/MdePkg/Include/Library/DebugLib.h b/MdePkg/Include/Library/DebugLib.h
index 40772f2e0f..bc7789f01c 100644
--- a/MdePkg/Include/Library/DebugLib.h
+++ b/MdePkg/Include/Library/DebugLib.h
@@ -426,7 +426,12 @@ UnitTestDebugAssert (
       }                            \
     } while (FALSE)
 #else
-#define DEBUG(Expression)
+#define DEBUG(Expression)        \
+    do {                           \
+      if (FALSE) {                 \
+        _DEBUG (Expression);       \
+      }                            \
+    } while (FALSE)
 #endif
 
 /**
-- 
2.39.2



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