Syntax

unary-expr  assignment-op  assignment-expr

Remarks 

The assignment operators are:

=    *=     /=     %=    +=    -=
<<=  >>=    &=     ^=    |=

The = operator is the only simple assignment operator, the others are compound assignment operators. 

In the expression E1 = E2, E1 must be a modifiable lvalue. The assignment expression itself is not an lvalue. 

The expression

E1 op= E2 

has the same effect as

E1 = E1 op E2

except the lvalue E1 is evaluated only once. For example, E1 += E2 is the same as E1 = E1 + E2. 

The expression's value is E1 after the expression evaluates. 

For both simple and compound assignment, the operands E1 and E2 must obey one of the following rules:

• 1. E1 is a qualified or unqualified arithmetic type and E2 is an arithmetic type.
• 2. E1 has a qualified or unqualified version of a structure or union type compatible with the type of E2.
• 3. E1 and E2 are pointers to qualified or unqualified versions of compatible types, and the type pointed to by the left has all the qualifiers of the type pointed to by the right.
• 4. Either E1 or E2 is a pointer to an object or incomplete type and the other is a pointer to a qualified or unqualified version of void. The type pointed to by the left has all the qualifiers of the type pointed to by the right.
• 5. E1 is a pointer and E2 is a null pointer constant.