are you sure that 4+4+1=9 ?

[TouEnMasm]

I have tested the STORAGE_PROPERTY_QUERY structure here his:

STORAGE_PROPERTY_QUERY   STRUCT
   PropertyId DWORD ?
   QueryType DWORD ?
   AdditionalParameters BYTE 1 dup (?)
STORAGE_PROPERTY_QUERY      ENDS

For each individual part of the structure the c++ agree with the size
stock = sizeof(STORAGE_PROPERTY_QUERY);      12
  stock = sizeof(mesure.PropertyId);                     4
  stock = sizeof(mesure.QueryType);                     4
  stock = sizeof(mesure.AdditionalParameters);     1

4+4+1=12    ???
I suppose that an alignment or a round is made for the byte.
How to do the same thing with masm ??????

[TouEnMasm]

to know where are added the three bytes for alignment ,I try to get the adress of each member of the structure.

DWORD TestSize(STORAGE_PROPERTY_QUERY * essai)
{
   STORAGE_PROPERTY_QUERY * machin;
    STORAGE_PROPERTY_QUERY * chose;

   chose = essai;                ok here,adress of the structure
   machin = * essai->PropertyId; ????? failed
   return 0;
}

Perhaps somebody here know how to get the adress of essai.PropertyId ?

[qWord]

to know where are added the three bytes for alignment ,I try to get the adress of each member of the structure.

The bytes are appended. To get a reference:  &essai->PropertyId.

[dedndave]

Code Select Expand

STORAGE_PROPERTY_QUERY   STRUCT DWORD
   PropertyId DWORD ?
   QueryType DWORD ?
   AdditionalParameters BYTE ?
STORAGE_PROPERTY_QUERY      ENDS

doesn't that work ???
otherwise - you might try the OPTION directive to set the structure alignment

if neither of those works....

Code Select Expand

STORAGE_PROPERTY_QUERY   STRUCT
   PropertyId DWORD ?
   QueryType DWORD ?
   AdditionalParameters BYTE ?
  BYTE 3 dup(?)
STORAGE_PROPERTY_QUERY      ENDS

:P

[MichaelW]

The attachment contains a C test and an ASM test. I think for structures that end with a 1-element array, the general expectation is that you allocate memory for the structure and use the structure definition as a template.

[TouEnMasm]

Ok , the & is an answer.
last question is , how i declare machin to made this work?
i have tried int dword ...

machin = (&essai - &essai->AdditionalParameters );

[MichaelW]

This should work:

Code Select Expand


int machin;
. . .
machin = ((int)&essai->PropertyId - (int)&essai->AdditionalParameters );
printf("%d\n\n", machin);


But if you want the offset of the AdditionalParameters member from the start of the structure you will need to reverse the subtraction, so the result will be 8 instead of -8.

[qWord]

The rules for aligment in structures can read up here: Structure Alignment

[japheth]

to get the offset of a member within a struct, the C offsetof() macro is probably the best choice:

mbrofs = offsetof( struct xxx, member );

[TouEnMasm]

Thanks at all for answers.
Here a resume of my test:

DWORD TestSize(STORAGE_PROPERTY_QUERY * essai)
{
    int machin;
    STORAGE_PROPERTY_QUERY * chose;
   chose = essai;
   machin = ((int)&essai->PropertyId - (int)&essai->AdditionalParameters );
   //machin = 8 or -8
   machin = offsetof( STORAGE_PROPERTY_QUERY,AdditionalParameters );
   // machin = 8 need  #include <stddef.h>
      return 0;
}

And for masm the good method to declare an alignment for a structure

STORAGE_PROPERTY_QUERY   STRUCT DWORD
   PropertyId DWORD ?
   QueryType DWORD ?
   AdditionalParameters BYTE 1 dup(?) ; dup (?)
STORAGE_PROPERTY_QUERY      ENDS   

This give the good size and the good alignment
I have learn much today.

[jj2007]

AdditionalParameters BYTE 1 dup(?) ; dup (?)
and
AdditionalParameters BYTE ?

are identical.

AdditionalParameters BYTE 4 dup(?)

achieves align DWORD, too.

[dedndave]

hiya Jochen
this one yields the correct result for SIZEOF AdditionalParameters

Code Select Expand

STORAGE_PROPERTY_QUERY   STRUCT
   PropertyId DWORD ?
   QueryType DWORD ?
   AdditionalParameters BYTE ?
  BYTE 3 dup(?)
STORAGE_PROPERTY_QUERY      ENDS

[TouEnMasm]

The interest of all this is to give at masm the correct alignment for each structure as do the c++.
here is a sample of translate,winhttp sample:

// defaut alignment for c++ is 4 ,DWORD for masm
#if defined(_WIN64)
#include <pshpack8.h>
#else
#include <pshpack4.h> //return to the defaut alignment
#endif
................ here structures ----------------------
#include <poppack.h>

can be done as this with masm

IF DEFINED(_WIN64)
;Include pshpack8.SDK
DEFALIGNMASM TEXTEQU <QWORD>
ELSE
;Include pshpack4.SDK
DEFALIGNMASM TEXTEQU <DWORD>
ENDIF
................ here structures ----------------------
     ANYSTRUCTURE STRUCT DEFALIGNMASM
        ..........
     ANYSTRUCTURE ENDS
;include <poppack.h>
DEFALIGNMASM TEXTEQU <DWORD>   ;return to defaut alignment

I have verify that this soluce work.
adding bytes to the structure isn't a good way

[japheth]

> I have verify that this soluce work.

It works most of the time, but AFAIR the Win32 alignment is also 8 (=QWORD), not DWORD.

It just doesn't matter usually because in Win32 there are very few QWORD members found in the structures.

But for an example where alignment DWORD doesn't work in Win32, see structure PARTITION_INFORMATION in winioctl.h.

So the simplest solution may just be to add -Zp8 as cmdline parameter when you want all Windows structures to be correct.

[TouEnMasm]

The Zp4 or Zp8 option are only a partial solution.
This don't avoid the "Invalid parameter" send by the function receiving a bad size of the structure.
With such an error,there is only to search , can be a long time.