Summary:
Clang analyzer was falsely reporting on use of txn=nullptr.
Added a new const variable so that it can properly prune impossible
control flows.
Also, 'make analyze' previously required setting USE_CLANG=1 as an
environment variable, not a make variable, or else compilation errors
like
g++: error: unrecognized command line option ‘-Wshorten-64-to-32’
Now USE_CLANG is not required for 'make analyze' (it's implied) and you
can do an incremental analysis (recompile what has changed) with
'USE_CLANG=1 make analyze_incremental'
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6244
Test Plan: 'make -j24 analyze', 'make crash_test'
Differential Revision: D19225950
Pulled By: pdillinger
fbshipit-source-id: 14f4039aa552228826a2de62b2671450e0fed3cb
95d226d8f5