If everyone is giving examples, of LD_PRELOAD — it has serious production use at scale in HPC, particularly for profiling and tracing. Runtimes such as MPI pro

If everyone is giving examples, of LD_PRELOAD — it has serious production use at scale in HPC, particularly for profiling and tracing. Runtimes such as MPI provide a layer designed for instrumentation to be interposed, typically with LD_PRELOAD (e.g. the standardized PMPI layer for MPI). Another example is the entirely userspace parallel filesystem that OrangeFS (né PVFS2) provides via the "userint" layer interposing on Unix i/o routines. That sort of facility is a major reason for using dynamic linking, despite the overheads of dynamically loading libraries for parallel applications at scale. I'm not sure if a solution could be hooked in with LD_PRELOAD, but Spindle actually uses LD_AUDIT: https://computation.llnl.gov/projects/spindle https://computation.llnl.gov/projects/spindle