为什么在 C11 中更改了 C99 中的此语句？
Why was this statement in C99 changed in C11?
C99 标准：
Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression
C11 标准：
If a side effect on a scalar object is unsequenced relative to another side effect on the same scalar object, the behavior is undefined.
C99 标准的这个定义是否不完整，因此在 C11 中进行了更新，因为它只包含术语 object 而不是 scalar object？
这是因为 C11 试图覆盖 multi-threading/parallel 执行。 "abstract machine"中程序执行的基本规则在C99和C11(C11 5.1.2.3/3)之间添加了这段繁琐的文字：
Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations
executed by a single thread, which induces a partial order among those evaluations.
Given any two evaluations A and B, if A is sequenced before B, then the execution of A
shall precede the execution of B. (Conversely, if A is sequenced before B, then B is
sequenced after A.) If A is not sequenced before or after B, then A and B are
unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced
either before or after B, but it is unspecified which.13) The presence of a sequence point
between the evaluation of expressions A and B implies that every value computation and
side effect associated with A is sequenced before every value computation and side effect
associated with B. (A summary of the sequence points is given in annex C.)
因此，您引用的部分 (C99 6.5/2) 已相应更改，以适应抽象机中程序执行的定义，据说现在也涵盖了并行执行。不幸的是 - 因为 C99 文本更具可读性。从技术上讲，如果您不考虑并行执行，则根本没有任何变化。 C99 中有关序列点的规则仍然适用，只是措辞不同。此更改还意味着将 C11 与具有类似规则的 C++11 同步。
C99 标准：
Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression
C11 标准：
If a side effect on a scalar object is unsequenced relative to another side effect on the same scalar object, the behavior is undefined.
C99 标准的这个定义是否不完整，因此在 C11 中进行了更新，因为它只包含术语 object 而不是 scalar object？
这是因为 C11 试图覆盖 multi-threading/parallel 执行。 "abstract machine"中程序执行的基本规则在C99和C11(C11 5.1.2.3/3)之间添加了这段繁琐的文字：
Sequenced before is an asymmetric, transitive, pair-wise relation between evaluations executed by a single thread, which induces a partial order among those evaluations. Given any two evaluations A and B, if A is sequenced before B, then the execution of A shall precede the execution of B. (Conversely, if A is sequenced before B, then B is sequenced after A.) If A is not sequenced before or after B, then A and B are unsequenced. Evaluations A and B are indeterminately sequenced when A is sequenced either before or after B, but it is unspecified which.13) The presence of a sequence point between the evaluation of expressions A and B implies that every value computation and side effect associated with A is sequenced before every value computation and side effect associated with B. (A summary of the sequence points is given in annex C.)
因此，您引用的部分 (C99 6.5/2) 已相应更改，以适应抽象机中程序执行的定义，据说现在也涵盖了并行执行。不幸的是 - 因为 C99 文本更具可读性。从技术上讲，如果您不考虑并行执行，则根本没有任何变化。 C99 中有关序列点的规则仍然适用，只是措辞不同。此更改还意味着将 C11 与具有类似规则的 C++11 同步。