[edk2-devel] RELEASE CLANGPDB OVMF currently does not compile

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

Dear Ard,

Thanks for your attention on my other issue, about NOOPT CLANGDWARF OVMF.

This one is about RELEASE CLANGPDB OVMF, which currently does not
compile, giving:

```
/home/mjsbeaton/OpenSource/edk2/OvmfPkg/VirtioSerialDxe/VirtioSerial.c:28:22:
error: variable 'EventNames' is not needed and will not be emitted
[-Werror,-Wunneeded-internal-declaration]
STATIC CONST CHAR8  *EventNames[] = {
                     ^
1 error generated.
```

I logged this at https://bugzilla.tianocore.org/show_bug.cgi?id=4620

This _can_ be fixed by:

```
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -1754,7 +1754,7 @@ DEFINE CLANGPDB_X64_PREFIX           = ENV(CLANG_BIN)
 DEFINE CLANGPDB_IA32_TARGET          = -target i686-unknown-windows-gnu
 DEFINE CLANGPDB_X64_TARGET           = -target x86_64-unknown-windows-gnu

-DEFINE CLANGPDB_WARNING_OVERRIDES    = -Wno-parentheses-equality
-Wno-tautological-compare
-Wno-tautological-constant-out-of-range-compare -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-microsoft-enum-forward-reference
+DEFINE CLANGPDB_WARNING_OVERRIDES    = -Wno-parentheses-equality
-Wno-tautological-compare
-Wno-tautological-constant-out-of-range-compare -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
-Wno-microsoft-enum-forward-reference
 DEFINE CLANGPDB_ALL_CC_FLAGS         = DEF(GCC48_ALL_CC_FLAGS)
DEF(CLANGPDB_WARNING_OVERRIDES) -fno-stack-protector -funsigned-char
-ftrap-function=undefined_behavior_has_been_optimized_away_by_clang
-Wno-address -Wno-shift-negative-value -Wno-unknown-pragmas
-Wno-incompatible-library-redeclaration -Wno-null-dereference
-mno-implicit-float -mms-bitfields -mno-stack-arg-probe -nostdlib
-nostdlibinc -fseh-exceptions

 ###########################
```

which duplicates https://github.com/tianocore/edk2/commit/d3225577123,
which already applied the same change to CLANGDWARF.

That change was discussed and approved here:
https://edk2.groups.io/g/devel/topic/98807494 - however, I'd like to
belatedly object, if I may!

There is currently exactly one line of code which needs this warning
to be disabled (at least, in OVMF), the line mentioned above. So if we
were going to bring the warning back, now rather than later would be
the time to do it. The issue at that line can, of course, be worked
around by removing the STATIC (and presumably adding a comment, so
that someone doesn't mistakenly add it back again).

I would guess that there must be several other places where people
_have_ already tiptoed round this issue before, in EDK-2 code, though
a quick search for the warning name itself only throws up one such
instance in OpenSslLib.

The advantage of tiptoeing round the issue (in the reasonably rare
cases where needed) instead of disabling the error check, is that the
check may well show up genuine issues in code (perhaps most obviously,
variables left unused after code changes).

For that reason, I'd propose re-enabling the warning in CLANGDWARF,
and removing the STATIC (and adding a comment) in the relevant line in
VirtioSerialDxe.


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