mcheckh

mcheckh is a command-line utility found on some Unix-like operating systems, particularly those derived from or inspired by System V. Its primary function is to check the integrity of memory, specifically focusing on the heap data structure. This can be a useful debugging tool for developers working with C or C++ programs that manage memory dynamically using functions like malloc and free.

When a program exhibits memory corruption issues, such as buffer overflows, use-after-free errors, or double frees, these problems can manifest in unpredictable ways. mcheckh can help identify these issues by performing checks on the memory allocated and deallocated by the C standard library's memory management functions. It works by inserting internal checks and metadata within the heap. When these checks are later invoked, they can detect inconsistencies that indicate memory corruption.

To use mcheckh, it is typically invoked by setting an environment variable, such as MALLOC_CHECK_, before running the program in question. Different values assigned to this variable can enable various levels of checking, from basic integrity tests to more thorough analysis. Upon detecting an error, mcheckh will usually print an error message to standard error, often indicating the type of corruption found and potentially a backtrace to help pinpoint the source of the problem. It's important to note that while mcheckh can be a valuable debugging aid, its overhead can impact program performance, making it more suitable for development and debugging phases rather than production environments.