[edk2-devel] [PATCH] DebugLib: Allow -Wunneeded-internal-declaration with clang

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

From: Mike Beaton <mjsbeaton@gmail.com>

Provides a variant of the DEBUG macro for clang when MDEPKG_NDEBUG is defined,
which uses but discards the contained expression, this means clang can tell
that it has optimised away variable usage, therefore we can keep
-Wunneeded-internal-declaration (as part of -Wall) to warn about any
mistakenly genuinely unused variables.

Signed-off-by: Mike Beaton <mjsbeaton@gmail.com>
---
 BaseTools/Conf/tools_def.template |  2 +-
 MdePkg/Include/Library/DebugLib.h | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

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 f0c9f64487..e2158b1a3d 100644
--- a/MdePkg/Include/Library/DebugLib.h
+++ b/MdePkg/Include/Library/DebugLib.h
@@ -425,6 +425,16 @@ UnitTestDebugAssert (
         _DEBUG (Expression);       \
       }                            \
     } while (FALSE)
+#elif defined (__clang__)
+#define DEBUG(Expression)                                \
+    do {                                                   \
+      _Pragma("GCC diagnostic push")                       \
+      _Pragma("GCC diagnostic ignored \"-Wunused-value\"") \
+      if ((FALSE)) {                                       \
+        (VOID) Expression;                                 \
+      }                                                    \
+      _Pragma("GCC diagnostic pop")                        \
+    } while (FALSE)
 #else
 #define DEBUG(Expression)
 #endif
-- 
2.39.2



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