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digitalmars.D.bugs - DMD .120 sizeof struct bug

reply dickl <dick221z yahoo.com> writes:
This appeared in .120 and worked in previous versions

The size of the struct should be 5 but is returned as 8.
Changing the struct to  "align(1) struct foo" gives the correct answer.

This has implications when passing structures to the Windows api.
-------------------------------------

private import std.stdio;
struct foo
{
	uint cbSize;
	char j;
}

int main()
{
	uint k=foo.sizeof; // k should be 5 but foo.sizeof returns 8
	return 0;

}
Apr 08 2005
next sibling parent Thomas Kuehne <thomas-dloop kuehne.thisisspam.cn> writes:
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dickl schrieb am Fri, 08 Apr 2005 23:00:53 -0400:

 This appeared in .120 and worked in previous versions

 The size of the struct should be 5 but is returned as 8.
 Changing the struct to  "align(1) struct foo" gives the correct answer.

 This has implications when passing structures to the Windows api.
 -------------------------------------

 private import std.stdio;
 struct foo
 {
 	uint cbSize;
 	char j;
 }

 int main()
 {
 	uint k=foo.sizeof; // k should be 5 but foo.sizeof returns 8
 	return 0;

 }



Seems to be missing from the changelog - this was documented in the
source code. I'm not sure that this solution to the GC problem is wise.

Thomas
 

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Apr 08 2005
prev sibling parent reply "Walter" <newshound digitalmars.com> writes:
"dickl" <dick221z yahoo.com> wrote in message
news:d37gh6$v1i$1 digitaldaemon.com...

 This appeared in .120 and worked in previous versions

 The size of the struct should be 5 but is returned as 8.
 Changing the struct to  "align(1) struct foo" gives the correct answer.

 This has implications when passing structures to the Windows api.



D was changed to match C's behavior, which gives 8 as well:

#include <stdio.h>

struct foo
{
    unsigned cbSize;
    char j;
};

void main()
{
    printf("%d\n", sizeof(struct foo));    // prints 8
}
Apr 09 2005
next sibling parent Carlos <carlos2003nov yahoo.ca> writes:
Walter wrote:

 "dickl" <dick221z yahoo.com> wrote in message
 
 D was changed to match C's behavior, which gives 8 as well:
 



True.

C:\> cl program.c
C:\> program
8

and:

C:\> cl -Zp1 program.c
C:\> program
5

-Zp{n} should be available in D.
DMD has not enough switches...
Apr 09 2005
prev sibling parent reply dickl <dick221z yahoo.com> writes:
Its fine as long as I know what it is doing and how to work around.

However, the code is from Microsoft DDK so the Microsoft compiler
is returning  5 rather than 8 and of course Windows was expecting 5.

Walter wrote:

 "dickl" <dick221z yahoo.com> wrote in message
 news:d37gh6$v1i$1 digitaldaemon.com...
 

This appeared in .120 and worked in previous versions

The size of the struct should be 5 but is returned as 8.
Changing the struct to  "align(1) struct foo" gives the correct answer.

This has implications when passing structures to the Windows api.



 
 D was changed to match C's behavior, which gives 8 as well:
 
 #include <stdio.h>
 
 struct foo
 {
     unsigned cbSize;
     char j;
 };
 
 void main()
 {
     printf("%d\n", sizeof(struct foo));    // prints 8
 }
Apr 09 2005
parent "Walter" <newshound digitalmars.com> writes:
"dickl" <dick221z yahoo.com> wrote in message
news:d38rub$kvh$1 digitaldaemon.com...

 Its fine as long as I know what it is doing and how to work around.

 However, the code is from Microsoft DDK so the Microsoft compiler
 is returning  5 rather than 8 and of course Windows was expecting 5.



Check the DDK code - I bet there's a #pragma pack(1) around the struct
declaration, which works like D's align(1).
Apr 09 2005