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Global variable alignment

Note: This was originally posted on 13th January 2011 at http://forums.arm.com

Hi,

I am working with RealView Compilation Tools v2.1. I need to align a static global variable on a 16-byte boundary. In the 'Compiler and Libraries Guide' document, section 3.1.3, the __align(n) keyword is explained. It is not clear to me if n=16 is allowed for a static global variable. I have tried it and it appears to be working, but I would like to confirm it.

Best Regards,
Miguel

Miguel Sebastián over 12 years ago

Note: This was originally posted on 17th January 2011 at http://forums.arm.com

Hi,

I have not received any answers, can someone help me on this?

Regards,
Miguel
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Miguel Sebastián over 12 years ago

Note: This was originally posted on 19th January 2011 at http://forums.arm.com

Hi,

The point is that RVCT 2.1 says: '[font="Times-Roman"][size="2"]You can specify a power of two for the alignment boundary, however eight is the maximum for auto variables'. As I understand, an 'auto' variable is the same as a 'local' variable, so it is not clear to me what is the limitation for global variables.

Regards,
Miguel[/size][/font]
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Peter Harris over 12 years ago
Note: This was originally posted on 17th January 2011 at http://forums.arm.com

For RVCT 2.1 it is only specified to work for alignments of 1,2,4, or 8 - it is unclear what happens for alignments larger than this, although I suspect it is not guaranteed to do anything predictably.

FYI - in newer tool releases (RVCT4.1) it will work for the following alignments of n:

For local variables, n can take the values 1, 2, 4, or 8.
For global variables, n can take any value up to 0x80000000 in powers of 2.
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