Previously, lexing and parsing errors were aggregated while CQL queries were
evaluated. Afterwards, the first collected error (if present) would be thrown as
an exception.
The problem was that when parsing and lexing errors were aggregated this way,
the parser would continue even in spite of errors like "no viable alternative".
Semantic actions attached to grammar rules would still execute, though with
variables that had not yet been initialized. This would crash Scylla.
This change modifies the error-handling strategy of CQL parsing. Rather than
aggregate errors, we throw an exception on the first error we encounter. This
ensures that grammar actions never execute unless there is a precise match.
One possible issue with this approach is that the generated C++ code from the
ANTLR grammar may not be exception-safe. I compiled Scylla in debug-mode with
ASan support and executed several erroneous CQL queries with `cqlsh`. No memory
leaks were reported.
Fixes#2466.
Signed-off-by: Jesse Haber-Kucharsky <jhaberku@scylladb.com>
Message-Id: <db1f650a2bbb615b506d9015486eece45375a440.1498836703.git.jhaberku@scylladb.com>
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