[jira] [Created] (PROTON-585) Can improve memory use by rearranging structs to eliminate padding

["Andrew Stitcher (JIRA)" <ji...@apache.org>]

Andrew Stitcher created PROTON-585:
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             Summary: Can improve memory use by rearranging structs to eliminate padding
                 Key: PROTON-585
                 URL: https://issues.apache.org/jira/browse/PROTON-585
             Project: Qpid Proton
          Issue Type: Improvement
          Components: proton-c
    Affects Versions: 0.6, 0.7
            Reporter: Andrew Stitcher
            Assignee: Andrew Stitcher
            Priority: Minor


The C/C++ language rules allow compilers to add extra padding in the middle of structs .Generally this is done to maintain the correct ABI alignment for the members.

This means that by paying attention to the sizes of the members you can eliminate the padding simply by putting the largest members (with the biggest alignment constraint) first then the next then the next down to bitfields (if you are using them).

Removing the padding can reduce the space used by structs and this can be significant if enough of them are allocated.



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