# Valgrind

**Valgrind** is a dynamic analysis framework that instruments your program to detect memory bugs, threading races, and performance issues. It runs your code on a synthetic CPU, observing every memory access and checking for errors: buffer overflows, use-after-free, memory leaks, uninitialized values, data races. Catches bugs at the moment they happen, not when they cause a crash elsewhere.

The trade-off: 10-50x slowdown due to instrumentation. Fine for testing and debugging; use [[perf]] for production profiling. Valgrind's memcheck tool is what most people use—compile with `-g -O0`, run `valgrind ./program`, and read the error report pointing to the exact line and function.

```bash
$ gcc -g -O0 -o program program.c
$ valgrind ./program
==12345== Invalid read of size 4
==12345==    at 0x109179: process (program.c:22)
==12345==  Address 0x4a4b080 is 0 bytes after a block of size 40 alloc'd
==12345==    at 0x483DD99: malloc (vg_replace_malloc.c:307)
==12345==    by 0x109150: process (program.c:15)
```

Invaluable for finding memory bugs that don't crash or leave obvious symptoms.

## Concepts

 1. [[valgrind-basics|Basics]]
 2. [[valgrind-memcheck|memcheck]]
 3. [[valgrind-output|Output]]
 4. [[valgrind-helgrind|helgrind]]
 5. [[valgrind-drd|DRD]]
 6. [[valgrind-callgrind|callgrind]]
 7. [[valgrind-cachegrind|cachegrind]]
 8. [[valgrind-massif|massif]]
 9. [[valgrind-suppressions|Suppressions]]
 10. [[valgrind-performance|Performance]]