Memcheck

Memcheck is a memory error detector within the Valgrind instrumentation framework. It checks programs for memory management problems in C, C++, and related languages by executing the program under Valgrind’s dynamic instrumentation. Memcheck can detect uninitialized reads, reads and writes to freed or unallocated memory, buffer overruns, and memory leaks, among other errors.

How Memcheck works: It uses a shadow memory model to track the state of every byte of the program’s memory. As the program runs, Memcheck records allocations and frees and checks each memory access against the shadow state. When an error is detected, Memcheck reports the location with stack traces if symbols are available. It can classify memory leaks into categories such as definitely lost, indirectly lost, possibly lost, and still reachable, and can track origins for uninitialized values with appropriate options.

Usage: Typical workflow is to compile with debugging symbols and run under Valgrind, for example: valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all ./program [args]. Optional flags include --track-origins=yes, --suppressions=, and --error-exitcode. Output consists of error messages detailing each issue and a summary of leaks at program exit, aiding developers in locating and fixing problems.

Limitations and scope: Memcheck detects many common memory errors but is not a general debugger and can miss some issues. It imposes substantial runtime overhead, making it unsuitable for production use. It may report false positives in some scenarios and usually requires debugging information to provide meaningful traces.

History and relation: Memcheck is the most widely used tool in the Valgrind suite, developed as part of the Valgrind project to help developers identify memory management bugs in software.