请教一个基础问题——数组名减1是否可以

nicolas.shen

标准要参考多方面的东西去理解，从数组去理解，下标非负数为标准，从指针的传递去理解，a-1也没问题，因为也许别人看不到这个数组，只能看到指针。自己定义了，自己去用才能知道是否是undefined behavior

OwnWaterloo

哦， 我以为你已经看过标准里说这是未定义行为了呢。

c99， 6.5.6 Additive operators

8
When an expression that has integer type is added to or subtracted from a pointer, the
result has the type of the pointer operand. If the pointer operand points to an element of
an array object, and the array is large enough, the result points to an element offset from
the original element such that the difference of the subscripts of the resulting and original
array elements equals the integer expression. In other words, if the expression P points to
the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
(P)-N (where N has the value n) point to, respectively, the i+n-th and i−n-th elements of
the array object, provided they exist. Moreover, if the expression P points to the last
element of an array object, the expression (P)+1 points one past the last element of the
array object, and if the expression Q points one past the last element of an array object,
the expression (Q)-1 points to the last element of the array object. If both the pointer
operand and the result point to elements of the same array object, or one past the last
element of the array object, the evaluation shall not produce an overflow; otherwise, the
behavior is undefined. If the result points one past the last element of the array object, it
shall not be used as the operand of a unary * operator that is evaluated.

zhaohongjian000

指向 那个位置 不会有任何问题，但是别去写。

不报内存错误不见的就是真的没错。