Be ready to split some hairs :).

Take the following struct

struct Bleh {
    mat4 a;
    vec3 b;
}

Crevice interprets this struct as being of size 76, via calling std140_size_static.

This goes against what both the wgsl and GL spec specify, asking for a size of 80 (roundUp(16, 64 + 12)). It also interprets this struct as size 80 instead of the proper size 96.

struct Other {
    Bleh a;
    f32 b;
}

wgsl:

The size of a structure is equal to the offset plus the size of its last member, rounded to the next multiple of the structure’s alignment:

SizeOf(S) = roundUp(AlignOf(S), OffsetOf(S, L) + SizeOf(S, L))
Where L is the last member of the structure 

GL:

The structure may have padding at the end;the base offset of the member following the sub-structure is rounded up to the next multiple of the base alignment of the structure.

This GL spec rules only applies to the context of it being a member. Wgsl specifies this for both being a member and a top level struct. The GL spec does not say the size of the struct when it is a top level struct. Because of this omission, it should be valid to always interpret the size of this struct as 80.

This should make everyone agree, then we can live a happy life away from all this hair splitting and spec reading.