结构和对齐问题 [英] structures and alignment issues

问题描述

struct a

{

int b;

char a;

int c;

}


在i386上，这个结构的大小将是12个字节，因为3个字节是

在a之后填充，以便c对齐4字节边界。


所以我怀疑的是


1）只有当我坚持这个时，才会发挥可控性问题/>
结构在一个架构上（对于ex i386）并尝试在不同的架构上读取

结构（对于前摩托罗拉系列）

解决方案

6月14日上午8:30，sil ... @ gmail.com写道：

struct a

{

int b;

char a;

int c;


}


在i386上，这个结构的大小将是12个字节，因为3个字节是

填充之后所以c对齐4字节边界。


所以我怀疑的是


1）只有当我在一个架构上保留这个

结构（对于ex i386）并尝试阅读

时，才会发挥可能性问题结构回到不同的架构上（对于前摩托罗拉系列）

我想澄清的另一件事是做所有的编译器对齐

结构成员使用自然对齐或者这一切都不同

从建筑到建筑

si **** @ gmail.com 写道：

struct a

{

int b;

char a;

int c;

}


在i386上，此结构的大小为12个字节，因为3个字节是在b之后填充，因此c在4字节边界上对齐。

这是一种可能的对齐。

所以我怀疑的是


1）只有当我在一个体系结构上保留这个

结构（对于ex i386）并尝试阅读
$ b $时，才会发挥可能性问题b结构回到不同的架构上（对于前摩托罗拉系列）

或者使用不同编译器或相同编译器的相同架构

有不同的选择。或者......


-

Ian Collins。

si **** @ gmail.com 写道：


| 1）只有当我坚持

|时才会发挥可能性问题这个结构在一个架构上（对于ex i386）并尝试阅读

|结构回到不同的架构上（前摩托罗拉

|系列）


不，它总是一个问题。考虑单个架构上的单个编译器如何处理这种结构的差异

被告知要优化速度与被告知要优化大小...


-

Morris Dovey

DeSoto Solar

德索托，爱荷华州美国
http://www.iedu.com/DeSoto/

struct a
{
int b;
char a;
int c;
}

On i386 the sizeof this structure would be 12 bytes,as 3 bytes are
padded after a so that c is aligned on 4byte boundary.

So the doubts that i have is

1) Does the poratbility issue come into play only when i persist this
structure on one architecture ( for ex i386) and try to read the
structure back on a different architecture(for ex motorola series)

解决方案

On Jun 14, 8:30 am, [e-mail] wrote:

struct a
{
int b;
char a;
int c;

}

On i386 the sizeof this structure would be 12 bytes,as 3 bytes are
padded after a so that c is aligned on 4byte boundary.

So the doubts that i have is

1) Does the poratbility issue come into play only when i persist this
structure on one architecture ( for ex i386) and try to read the
structure back on a different architecture(for ex motorola series)

One more thing i want to get clarified is do all the compilers align
structure members using natural alignement or does this all differ
from architecture to architecture

si****@gmail.com wrote:

struct a
{
int b;
char a;
int c;
}

On i386 the sizeof this structure would be 12 bytes,as 3 bytes are
padded after a so that c is aligned on 4byte boundary.

That''s one possible alignment.

So the doubts that i have is

1) Does the poratbility issue come into play only when i persist this
structure on one architecture ( for ex i386) and try to read the
structure back on a different architecture(for ex motorola series)

Or the same architecture with a different compiler, or the same compiler
with different options. Or...

--
Ian Collins.

si****@gmail.com wrote:

| 1) Does the poratbility issue come into play only when i persist
| this structure on one architecture ( for ex i386) and try to read
| the structure back on a different architecture(for ex motorola
| series)

No, it can always be an issue. Consider the differences in how a
single compiler on a single architecture might treat this structure
when told to optimize for speed vs when told to optimize for size...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

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