Consistency checks

Inconsistent use of variables, arguments, and functions is checked within files as well as across them. Generally speaking, the same checks are performed for prototype uses, declarations, and parameters as for old-style functions. (If your program does not use function prototypes, lint will check the number and types of parameters in each call to a function more strictly than the compiler.) lint also identifies mismatches of conversion specifications and arguments in [fs]printf and [fs]scanf control strings. Examples:

• Within files, lint flags nonvoid functions that ``fall off the bottom'' without returning a value to the invoking function. In the past, programmers often indicated that a function was not meant to return a value by omitting the return type: fun() {}. That convention means nothing to the compiler, which regards fun as having the return type int. Declare the function with the return type void to eliminate the problem.

• Across files, lint detects cases where a nonvoid function does not return a value, yet is used for its value in an expression, and the opposite problem, a function returning a value that is sometimes or always ignored in subsequent calls. When the value is always ignored, it may indicate an inefficiency in the function definition. When it is sometimes ignored, it's probably bad style (typically, not testing for error conditions). If you do not need to check the return values of string functions like strcat, strcpy, and sprintf, or output functions like printf and putchar, cast the offending call(s) to void.

• lint identifies variables or functions that are declared but not used or defined; used but not defined; or defined but not used. That means that when lint is applied to some, but not all files of a collection to be loaded together, it will complain about functions and variables declared in those files but defined or used elsewhere; used there but defined elsewhere; or defined there and used elsewhere. Invoke the -x option to suppress the former complaint, -u to suppress the latter two.