Placing spaces

Betty coding style for use of spaces depends (mostly) on function-versus-keyword usage.
Use a space after (most) keywords.
The notable exceptions are sizeof, typeof, alignof, and __attribute__, which look somewhat like functions.

So use a space after these keywords:

	if, else if, switch, case, for, while, return

but not with sizeof, typeof, alignof, or __attribute__.

Keyword	Space After	Example
if	Yes	if (condition)
else if	Yes	else if (condition)
switch	Yes	switch (variable)
case	Yes	case value:
for	Yes	for (i = 0; i < 10; ++i)
while	Yes	while (condition)
return	Yes	return (1);
sizeof	No	sizeof(struct file)
typeof	No	typeof(variable)
alignof	No	alignof(variable)
__attribute__	No	__attribute__((unused))

Do not add spaces around (inside) parenthesized expressions.
This example is bad:

	s = sizeof( struct file );

When declaring pointer data or a function that returns a pointer type, the preferred use of * is adjacent to the data name or function name and not adjacent to the type name.
Examples:

	char *str;
	unsigned int sample(char *ptr, char **retptr);
	char *match_strdup(substring_t *s);

Use one space around (on each side of) most binary and ternary operators, such as any of these:

	=  +  -  <  >  *  /  %  |  &  ^  <=  >=  ==  !=  ?  :

but no space after unary operators:

	&  *  +  -  ~  !  sizeof  typeof  alignof  __attribute__  defined

no space before the postfix increment & decrement unary operators:

	++  --

Example:

int i;

i = 0;
i++;
i--;

no space after the prefix increment & decrement unary operators:

	++  --

Example:

int i;

i = 0;
++i;
--i;

and no space around the . and -> structure member operators.

Do not leave trailing whitespace at the ends of lines.
Some editors with smart indentation will insert whitespace at the beginning of new lines as appropriate, so you can start typing the next line of code right away. However, some such editors do not remove the whitespace if you end up not putting a line of code there, such as if you leave a blank line.
As a result, you end up with lines containing trailing whitespace.

Git will warn you about patches that introduce trailing whitespace, and can optionally strip the trailing whitespace for you; however, if applying a series of patches, this may make later patches in the series fail by changing their context lines.