https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65098
--- Comment #1 from vries at gcc dot gnu.org ---
This would fix it:
...
diff --git a/gcc/ada/gnat_rm.texi b/gcc/ada/gnat_rm.texi
index 04f3d0b..1fd0534 100644
--- a/gcc/ada/gnat_rm.texi
+++ b/gcc/ada/gnat_rm.texi
@@ -8886,7 +8886,7 @@ attribute.
prefix) yields a static string identifying the version of the compiler
being used to compile the unit containing the attribute reference. A
typical result would be something like
-"@value{EDITION} @value{gnat_version} (20090221)".
+"@value{EDITION} @value{version-GCC} (20090221)".
@node Attribute Constrained
@unnumberedsec Attribute Constrained
...
