The main source of big allocations in the WASM UDF implementation
is the WASM Linear Memory. We do not want Scylla to crash even if
a memory allocation for the WASM Memory fails, so we assert that
an exception is thrown instead.
The wasmtime runtime does not actually fail on an allocation failure
(assuming the memory allocator does not abort and returns nullptr
instead - which our seastar allocator does). What happens then
depends on the failed allocation handling of the code that was
compiled to WASM. If the original code threw an exception or aborted,
the resulting WASM code will trap. To make sure that we can handle
the trap, we need to allow wasmtime to handle SIGILL signals, because
that what is used to carry information about WASM traps.
The new test uses a special WASM Memory allocator that fails after
n allocations, and the allocations include both memory growth
instructions in WASM, as well as growing memory manually using the
wasmtime API.
Signed-off-by: Wojciech Mitros <wojciech.mitros@scylladb.com>
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