local directive-Masm x64

[OlivierS]

Hello,

there is something i cannot understand in the listing below (local directive, this is an excerpt of an lst file): why the localB variable  offset is a multiple of localB size (word: 2 bytes, offset= EBP-4), and, on the other hand, why pointer variable offset is not a multiple of pointer size (qword: 8 bytes, offset EBP-34h, that is EBP-52). Could someone explain me how the offsets get computed? I cant understand this clearly.

Code Select Expand

  vara . . . . . . . . . . . . . Byte rbp - 00000001
  localb . . . . . . . . . . . . Word rbp - 00000004
  dwv. . . . . . . . . . . . . . DWord rbp - 00000008
  QwArray. . . . . . . . . . . . QWord rbp - 00000028
  rlocal . . . . . . . . . . . . DWord rbp - 0000002C
  pointer. . . . . . . . . . . . QWord rbp - 00000034
 

I hope i posted this message in the right forum section, if that's not the case I apologize for the inconvenience.

Thanks!

Olivier

[zedd]

Does anyone that works with 64 bit code want to help our new friend Olivier?

I am dedicated 32 bit guy myself...
@ Olivier: Yes, this is the right place to ask questions while you are learning.

[jj2007]

Hi Olivier,
It's an alignment issue. I assume you are using this:

Code Select Expand

Local vara:BYTE, localb:WORD, dwv:DWORD, QwArray:QWORD, rlocal:DWORD, pointer:QWORDWhen you start the list with a BYTE variable, the assembler leaves some empty space to ensure that the following variables are at least DWORD aligned.

You should change the order, leaving the smaller sizes at the end.

[OlivierS]

Hi, and thanks a lot for your answer