Build Warning: Implicit Declarations

    QA Notice: Package has poor programming practices which may compile
               fine but exhibit random runtime failures.
    ...: warning: implicit declaration of function ...
    ...: warning: incompatible implicit declaration of built-in function ...
   

Your code is calling functions which lack prototypes. In C++, this would have been a build failure, but C is lazy so you just get a warning. This can be a problem as gcc has to guess at what sort of arguments a function takes based upon how it was called and often times, this is not the same as what the function actually takes. The function return type is also unknown so it's just assumed to be an integer (which is often times wrong). This can get to be a problem when the size of the types guessed do not actually match the size of the types the function expects. Generally, this corresponds directly to proper coding practices (and the lack thereof). Also, by including proper prototypes, the compiler often helps by checking types used, proper number of arguments passed, etc...

To fix this, just include the proper header files for the functions in question. If the function is a package-specific one, then you may have to create a header/function prototype for it.