Document STATIC_ASSERT; add STATIC_ASSERT_EXPR #23627
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khwilliamson
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tonycoz
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There are now enough items, that sorting is helpful to reading
The next commit will want this
I think these are useful and stable enough to make public
I found these useful in understanding it
These make things a bit clearer by not putting so much in each macro
This new type of a STATIC_ASSERT is used where an expression can go; hence potentially in macro expansions. Since it is compile-time, it can't be used on arguments that are expressions with side effects, so can safely be used in macros. It has limitations however, only reaching full parity when gcc brace groups are enabled, turning into an ASSUME which is a no-op in the worst case. However, most code will get compiled on a platform with gcc brace groups, and will pass or fail at compile time; so the chances of something bad actually getting into the field are minimal.
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The STATIC_ASSERT macros are useful and have been stable for long enough to be made API.
This also adds
STATIC_ASSERT_EXPRsuitable for use in macros. It doesn't achieve parity with the others except on systems where gcc brace groups are used, falling back to less or no checking otherwise. But that's good enough to be useful and any problems will be caught when the code is attempted to be compiled on a brace group platform.