Intel XENIX 286 Programmers Guide (86) - Tenox.tc

XENIX Programming lint: C Program Checker
Note that the lint program does not report a variable or function unused if it is
explicitly declared with the extern storage class. Such a variable or function is assumed
to be used in another source file.
You can direct lint to ignore all the external declarations in a source file by using the -x
{for "external") option. The option causes the program checker to skip any line that
begins with the extern storage class.
The option is typically used to save time when checking a program, especially if all
external declarations are known to be valid.
Some programming styles require functions that perform closely related tasks to have
the same number and type of arguments regardless of whether or not these arguments
are used. Under normal operation, lint reports any argument not used as an unused
variable, but you can direct lint to ignore unused arguments by using the -v option. The
-v option causes lint to ignore all unused function arguments except for those declared
with register storage class. The program considers unused arguments of this class to be
a preventable waste of the register resources of the computer.
You can direct lint to ignore all unused variables and functions by using the -u {for
"unused") option. This option prevents lint from reporting variables and functions it
considers unused.
This option is typically used when checking a source file that contains just a portion of a
large program. Such source files usually contain declarations of variables and functions
to be used in other source files that are not explicitly used within the file. Since lint can
check only the given file, it normally assumes that such variables or functions are
unused and reports them as errors.
Checking Local Variables
The lint program checks all local variables to see that they are set to a value before
being used. Since local variables have either automatic or register storage class, their
values at the start of the program or function cannot be known. Using such a variable
before assigning a value to it is an error.
The program checks the local variables by searching for the first assignment in which
the variable receives a value and the first statement or expression in which the variable
is used. If the first assignment appears later than the first use, lint considers the
variable inappropriately used. For example, in the program fragment
int c;
if ( c ! = EOT )
c = getchar( );
lint warns that the the variable c is used before it is assigned.
3-3