ANSI C program memory check with valgrind

Over the years, ANSI C has been my selected language for scientific computations, from SCHNAaP/SCHNArP, 3DNA, to my current research projects. As noted by K&R in the preface of "The C Programming Language" book (2nd edition), C "wears well as one's experience with it grows". To me, ANSI C is a language that the better I know it, the more I love it.

Using gcc with strict compiler options -ansi -pedantic -Werror -Wall -W -Wshadow, my ANSI C programs (e.g., 3DNA) compile cleanly without any change on all the OSes I have access to. Any C programmer should be well aware of the memory leak type of bugs that are so difficult to fix, since it is not checked by gcc. That's where valgrind comes in and I have been using it in 3DNA and my current projects on a regular basis.

The usefulness of the valgrind toolset becomes obvious when a SCHNArP user posted a question about some possible memory leak bugs. Traditionally, SCHNArP works interactively from command line and builds one model (DNA structure) at a time. When the program exists, any meomry leaks are reclaimed by the system so such bugs do not show up. At the time SCHNAaP/SCHNArP was developed, I was not aware of valgrind (or maybe it even did not exist yet!). The user has been using some functions from SCHNArP to build many structures automatically, thus any small amount of memory leaks scales up and eventually aborts out-of-memory. As a test case, the user supplied me with a reproducible example as follows:

    while(1){
        GLH_build();    
    }

Without knowing of valgrind and actually applied it in this situation, fixing such bugs would have been too time consuming than I could manage to spend. However, with the help of valgrind, solving this puzzle did not take that long at all. More specifically, recompiling the sample program with -g option to have debug information, and running it with valgrind --leak-check=full prefixed immediately revealed a couple of locations with memory leaks. Knowing where the problems are, fixing them became straightforward. Now SCHNArP is more robust.

Overall, valgrind is an essential tool for any serious C programers.