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copied!<p>Imagine</p> <pre><code>#define CACHE_LINE_SIZE 32 sizeof(T) == 48 </code></pre> <p>Now, consider how <code>[[ align(CACHE_LINE_SIZE) ]]</code>, works. eg:</p> <pre><code>[[ align(32) ]] Foo foo; </code></pre> <p>This will force <code>sizeof(Foo) == 32n</code> for some <code>n</code>. ie align() will pad for you, if necessary, in order for things like <code>Foo foo[10];</code> to have each <code>foo[i]</code> aligned as requested.</p> <p>So, in our case, with <code>sizeof(T) == 48</code>, this means <code>sizeof(cache_line_storage<T>) == 64</code>.</p> <p>So the alignment gives you the padding you were hoping for.</p> <p>However, this is one 'error' in the template. Consider this case:</p> <pre><code>#define CACHE_LINE_SIZE 32 sizeof(T) == 32 </code></pre> <p>Here we end up with <code>char pad[1];</code>. Which means <code>sizeof(cache_line_storage<T>) == 64</code>. Probably not what you want!</p> <p>I think the template would need to be modified somewhat:</p> <pre><code>template <typename T, int padding> struct pad_or_not { T data; char pad[padding]; }; // specialize the 0 case // As it is late, I am SURE I've got the specialization syntax wrong... template <typename T, int> struct pad_or_not<0> { T data; }; template<typename T> struct cache_line_storage { [[ align(CACHE_LINE_SIZE) ]] pad_or_not<T, (sizeof(T) > CACHE_LINE_SIZE ? 0 : CACHE_LINE_SIZE - sizeof(T) ) > data; }; </code></pre> <p>or something like that.</p>

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