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valgrind

Use when running Valgrind Memcheck for heap errors, leaks, or uninitialised reads on an unmodified binary, or Cachegrind, Callgrind, or Massif profiling. Not for ASan builds: use sanitizers.

.devin/skills/valgrind/SKILL.md

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Apache-2.0

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# Valgrind

Valgrind (current stable 3.27.1) runs an unmodified binary on a synthetic CPU and instruments every memory access. Four tools matter here: Memcheck finds memory errors and leaks, Cachegrind simulates the cache, Callgrind records exact call counts and inclusive costs, and Massif samples the heap over time. Nothing needs recompiling, so Valgrind is the tool when the build cannot be changed or when uninitialised-value tracking is the question.

## Contract

| Field | Bound contract |
|---|---|
| Trigger | A native program corrupts the heap, leaks, reads uninitialised memory, or needs cache, call-count, or heap-growth profiling, and the user cannot or does not want to rebuild with sanitizers. |
| Authority | Reversible local: writes only Valgrind output files (`cachegrind.out.*`, `callgrind.out.*`, `massif.out.*`, `--log-file` targets, suppression files) and the test binary in the working directory; rollback is deleting them. No remote mutation. |
| Side effect | Output files on disk. The program runs 10 to 50 times slower under Memcheck (Valgrind's own figure), so long workloads need trimming. |
| Done | Each reported error is classified with its source line, each leak record carries its kind, and the exit code reflects the error count when `--error-exitcode` is set. Profiling runs end with an annotated report naming the top functions or the peak heap snapshot. |

## Inputs