将union的字段传递给函数 [英] passing a union's field to a function
问题描述
你好！
下面的示例程序由gcc（带-Wall）编译好，但被Sun的SUNWspro编译器拒绝了
（版本6更新2）。
争论的焦点是，一个联盟的类型的值是否可以将
传递给一个函数直接 - 没有创建一个单独的变量
联合类型并指定它的相应字段。
gcc过于宽松，还是这种行为只是Sun的旧编译器不支持的更新的b / b $ C标准的一部分？谢谢！
-mi
Mikhail Teterin说：
你好！
下面的示例程序由gcc（带-Wall）编译好，但
被Sun拒绝s SUNWspro编译器（版本6更新2）。
什么样本程序？
争论的焦点是，是否为其中一个联盟的值's
类型可以直接传递给函数 - 不需要创建union类型的单独的
变量并指定它的相应字段。
最近分配的union成员对象的值可以直接传递给
函数。没有必要将其复制出来。
gcc过于宽松，或者这种行为只是新行为的一部分
C-标准，Sun的旧编译器不支持？谢谢！
谁知道？我没有看到你的代码。
-
Richard Heathfield
Usenet是一个奇怪的地方 - dmr 29/7/1999
http://www.cpax.org.uk
电子邮件：rjh在上面的域名（但显然放弃了www）
Richard Heathfield写道：
< blockquote class =post_quotes>
什么样的程序？
您的新闻阅读器必须做一些令人讨厌的附件。
该程序附在原始帖子上。这里是内联的。
-mi
#include< stdio.h>
typedef union {
???????? int ????? i;
???????? void ???? * p;
???????? struct {
??????????????? int ?????我;
????????????????????????????????????????????????????????????? } ??????? s;
} testunion;
static void
testfunc（testunion u）
{
???????? printf（" i：％d \ np：％p \ n"，ui，up）;
}
int
main（）
{
??? ????? testfunc（（testunion）3）;
???????? testfunc（（testunion）NULL）;
????? ???返回0;
}
Mikhail Teterin说：
Richard Heathfield写道：
>什么样本程序？
您的新闻阅读器必须做一些令人讨厌的附件。
附件不会发生在comp.lang.c中 - 它是一个纯文本新闻组。
#include< stdio.h>
typedef union {
int i;
void * p;
struct {
int i;
int j;
} s;
} testunion;
static void
testfunc（testunion u）
{
printf（ i：％d \ np：％p \ n，ui，up）;
要么输入一个int，在这种情况下打印int是可以的，但不是
void *，或者你输入了一个空格*，在这种情况下可以打印
void *而不是int。
}
int
main（）
{
testfunc（（testunion）3）;
这不是有效的转换。
testfunc（（testunion）NULL）;
也不是。
返回0;
}
-
Richard Heathfield
Usenet是一个奇怪的地方 - dmr 29/7/1999
http://www.cpax.org.uk
电子邮件：rjh在上面的域名（但显然放弃了www）
Hello!
The sample program below is compiled fine by gcc (with -Wall), but rejected
by Sun''s SUNWspro compiler (version 6 update 2).
The point of contention is, whether a value for one of the union''s types can
be passed to a function directly -- without creating a separate variable of
the union type and assigning the appropriate field of it.
Is gcc being too liberal, or is this behavior simply part of a newer
C-standard, which Sun''s old compiler is not supporting? Thanks!
-mi
Mikhail Teterin said:
Hello!
The sample program below is compiled fine by gcc (with -Wall), but
rejected by Sun''s SUNWspro compiler (version 6 update 2).What sample program?
The point of contention is, whether a value for one of the union''s types
can be passed to a function directly -- without creating a separate
variable of the union type and assigning the appropriate field of it.The value of the most recently assigned union member object can be passed to
a function directly. There is no need to copy it out.
Is gcc being too liberal, or is this behavior simply part of a newer
C-standard, which Sun''s old compiler is not supporting? Thanks!Who knows? I don''t see your code.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)
Richard Heathfield wrote:What sample program?Your news-reader must be doing something nasty with attachments.
The program was attached to the original posting. Here it is inline.
-mi
#include <stdio.h>
typedef union {
????????int?????i;
????????void????*p;
????????struct {
????????????????int?????i;
????????????????int?????j;
????????}???????s;
} testunion;
static void
testfunc(testunion u)
{
????????printf("i: %d\np: %p\n", u.i, u.p);
}
int
main()
{
????????testfunc((testunion)3);
????????testfunc((testunion)NULL);
????????return 0;
}
Mikhail Teterin said:
Richard Heathfield wrote:>What sample program?
Your news-reader must be doing something nasty with attachments.Attachments don''t happen in comp.lang.c - it''s a text-only newsgroup.
#include <stdio.h>
typedef union {
int i;
void *p;
struct {
int i;
int j;
} s;
} testunion;
static void
testfunc(testunion u)
{
printf("i: %d\np: %p\n", u.i, u.p);Either you put in an int, in which case it''s okay to print the int but not
the void *, or you put in a void *, in which case it''s okay to print the
void * but not the int.
}
int
main()
{
testfunc((testunion)3);That''s not a valid conversion.
testfunc((testunion)NULL);Neither is that.
return 0;
}--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)
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