Reporting of memory accesses at a specific address
This function instructs DRD to log any load or store operation that overlaps the
**single byte** at `addr`.
Tracing is immediate. The returned guard manages the duration: tracing stops
automatically when the guard is dropped.
Corresponds to the `ANNOTATE_TRACE_MEMORY` client request.
# Mechanics
Contrast this with [`trace_var`](trace_var), which monitors the full size of a
variable (`sizeof::<T>`). This request is strictly a **1-byte trace**. It is
useful when you need to monitor activity at a specific pointer location without
a known or bounded type size, or when isolating a specific byte within a larger
structure (e.g., a packed field or a buffer offset).
## Note
Requires Valgrind **3.3** or higher.