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TI Home » TI E2E Community » Support Forums » Development Tools » TI C/C++ Compiler » TI C/C++ Compiler - Forum » #pragma STRUCT_ALIGN usage
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#pragma STRUCT_ALIGN usage

#pragma STRUCT_ALIGN usage

This question is answered
leemingu
Posted by leemingu
on Feb 21 2011 01:16 AM
Prodigy10 points

Hi...

I read the document about SPRU187Q.pdf..

In the PDF #pragma STRUCT_ALIGN( type, expression)...

I made a one stuct type like below

typedef  struct RCX_FILE_DOWNLOAD_REQ_DATA_Ttag
{
 unsigned  int                          ulXferType;             
  unsigned  int                          ulMaxBlockSize;         
unsigned  int                            ulFileLength;           
unsigned  int                             ulChannelNo;            
unsigned  short                        usFileNameLength;       
  }  RCX_FILE_DOWNLOAD_REQ_DATA_T;

#pragma STRUCT_ALIGN (RCX_FILE_DOWNLOAD_REQ_DATA_T, 2); 

and then...

Sizeof( RCX_FILE_DOWNLOAD_REQ_DATA_T)  ==>  Value is 20...

I expected it may be the 18...

What's wrong with that..?...

 

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  • Archaeologist
    Posted by Archaeologist
    on Feb 21 2011 11:19 AM
    Verified Answer
    Verified by George Mock
    Mastermind40550 points

    The pragma is ignored because it is less than the required natural alignment of the struct. 

    The compiler automatically pads structures to a multiple of the alignment, so you get 2 bytes of padding.

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