Generic scoped RAII guard for client requests
This struct manages the lifecycle of Valgrind requests, meant to be used in
pairs, defining a logical span.
The guard internally maps to the following Valgrind client request pairs:
- **Suppression:** `DRD_IGNORE_VAR` / `DRD_STOP_IGNORING_VAR`
- **Tracing:** `DRD_TRACE_VAR` / `ANNOTATE_TRACE_MEMORY` /
`DRD_STOP_TRACING_VAR`
- **Global Suppression:** `ANNOTATE_IGNORE_READS_BEGIN` /
`ANNOTATE_IGNORE_READS_END`, `ANNOTATE_IGNORE_WRITES_BEGIN` /
`ANNOTATE_IGNORE_WRITES_END`
- **Error reporting:** `VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE` /
`VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE`,
`VALGRIND_ENABLE_ERROR_REPORTING` / `VALGRIND_DISABLE_ERROR_REPORTING`
The guard never holds an active borrow (`&T`). It operates on the raw address,
so the borrow checker permits `&mut` access to the variable while the guard is
active.
# Safety
The guard operates only on raw memory addresses, not Rust variable bindings. If
the variable is moved or dropped while the guard exists, suppression/tracing
remains active on the **original** address.
Some requests (like
[`memcheck::disable_reporting`](memcheck::disable_reporting)) affect the whole
thread. They should logically be singletons. We can't enforce this in the type
system, so it's on you to ensure you aren't running multiple global guards at
once.
Likewise, nothing stops you from creating two guards for the same operation over
the same memory address. That will almost certainly break things.