Annex G (informative) Ill-formed, no diagnostic required [ifndr]

G.6 [dcl]: Declarations [ifndr.dcl]

G.6.7[ifndr:dcl.align.diff.translation.units]
Specified in: [dcl.align]

1
#
No diagnostic is required if declarations of an entity have different alignment-specifiers in different translation units.
2
#
[Example 1: 

Translation unit #1:struct S { int x; } s, *p = &s;

Translation unit #2:struct alignas(16) S; // IFNDR, definition of S lacks alignment extern S* p; — end example]