[lmi] -W[no-]unused-variable [Was: Getting rid of the rest of Boost]

[Greg Chicares]

On 10/24/21 11:31 AM, Vadim Zeitlin wrote:
[...]
>  One thing that I couldn't do in this commit was to remove the
> 
>     LMI_CXX_ADD_IF_SUPPORTED(-Wno-unused-variable)
> 
> line from configure. It was initially added as a workaround for warnings in
> Boost, but removing it now uncovered that this warning also occurs for "f2"
> and "f4" local variables in Ledger::make_evaluator().

Just now, I experimentally added that warning in 'workhorse.make':

   gcc_version_specific_cxx_warnings := \
     -Wredundant-tags \
+    -Wunused-variable \
     -Wvolatile \

and rebuilt with pc-linux-gnu gcc-10.x, but didn't see any warning:

  g++ -MMD -MP -MT ledger_evaluator.o -MF ledger_evaluator.d  -c [...]
 -Wzero-as-null-pointer-constant  -Wcast-qual  -Wredundant-tags 
-Wunused-variable -Wvolatile
 -O2 -fno-omit-frame-pointer -ggdb  -fPIC   
/opt/lmi/src/lmi/ledger_evaluator.cpp -oledger_evaluator.o

Any idea why?

I'd like to test and compare several ideas for fixing it, but
first I'd like to be able to reproduce it.