ISO/IEC9899:TC3
6.5.16 Assignment operators
Semantics
3 An assignment operator stores a value in the object designated by the left operand. An
assignment expression has the value of the left operand after the assignment, but is not an
lvalue. The type of an assignment expression is the type of the left operand unless the
left operand has qualified type, in which case it is the unqualified version of the type of
the left operand. The side effect of updating the stored value of the left operand shall
occur between the previous and the next sequence point.

JISX3010 同パラグラフ
代入演算子は、左オペランドで指し示されるオブジェクトに値を格納する。代入式は、代入後の
左オペランドの値をもつが、左辺値ではない。(以下略)

"An assignment expression has the value of the left operand after the assignment, but is not an lvalue."
・代入式は、"代入後の"左オペランドの値をもつ。代入後 (after the assignment) であって、代入前ではない