Please explicitly declare all arguments to functions.
Don't omit them just because they are int
s.
Declarations of external functions and functions to appear later in the
source file should all go in one place near the beginning of the file
(somewhere before the first function definition in the file), or else
should go in a header file. Don't put extern
declarations inside
functions.
It used to be common practice to use the same local variables (with
names like tem
) over and over for different values within one
function. Instead of doing this, it is better declare a separate local
variable for each distinct purpose, and give it a name which is
meaningful. This not only makes programs easier to understand, it also
facilitates optimization by good compilers. You can also move the
declaration of each local variable into the smallest scope that includes
all its uses. This makes the program even cleaner.
Don't use local variables or parameters that shadow global identifiers.
Don't declare multiple variables in one declaration that spans lines. Start a new declaration on each line, instead. For example, instead of this:
int foo, bar;
write either this:
int foo, bar;
or this:
int foo; int bar;
(If they are global variables, each should have a comment preceding it anyway.)
When you have an if
-else
statement nested in another
if
statement, always put braces around the if
-else
.
Thus, never write like this:
if (foo) if (bar) win (); else lose ();
always like this:
if (foo) { if (bar) win (); else lose (); }
If you have an if
statement nested inside of an else
statement, either write else if
on one line, like this,
if (foo) ... else if (bar) ...
with its then
-part indented like the preceding then
-part,
or write the nested if
within braces like this:
if (foo) ... else { if (bar) ... }
Don't declare both a structure tag and variables or typedefs in the same declaration. Instead, declare the structure tag separately and then use it to declare the variables or typedefs.
Try to avoid assignments inside if
-conditions. For example,
don't write this:
if ((foo = (char *) malloc (sizeof *foo)) == 0) fatal ("virtual memory exhausted");
instead, write this:
foo = (char *) malloc (sizeof *foo); if (foo == 0) fatal ("virtual memory exhausted");
Don't make the program ugly to placate lint
. Please don't insert any
casts to void
. Zero without a cast is perfectly fine as a null
pointer constant.