I've checked in this patch for PR 53608. It's derived from the text
suggested in the issue.
-Sandra
2018-11-22 Sandra Loosemore <san...@codesourcery.com>
Alan Coopersmith <alan.coopersm...@oracle.com>
PR c/53608
gcc/
* doc/extend.texi (Designated Inits): Clarify handling of multiple
initializers for unions.
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 266400)
+++ gcc/doc/extend.texi (working copy)
@@ -2104,7 +2104,7 @@ Another syntax that has the same meaning
struct point p = @{ y: yvalue, x: xvalue @};
@end smallexample
-Omitted field members are implicitly initialized the same as objects
+Omitted fields are implicitly initialized the same as for objects
that have static storage duration.
@cindex designators
@@ -2162,11 +2162,13 @@ example, with the @samp{struct point} de
struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @};
@end smallexample
-@noindent
-If the same field is initialized multiple times, it has the value from
-the last initialization. If any such overridden initialization has
-side effect, it is unspecified whether the side effect happens or not.
-Currently, GCC discards them and issues a warning.
+If the same field is initialized multiple times, or overlapping
+fields of a union are initialized, the value from the last
+initialization is used. When a field of a union is itself a structure,
+the entire structure from the last field initialized is used. If any previous
+initializer has side effect, it is unspecified whether the side effect
+happens or not. Currently, GCC discards the side-effecting
+initializer expressions and issues a warning.
@node Case Ranges
@section Case Ranges
