@@ -118,6 +118,35 @@ is assigned the address of a function
 instead of prefixing the message with the program name and colon.
 The function should print a suitable string to
 .IR stderr .
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lb lb lbw37
+l l l.
+Interface	Attribute	Value
+T{
+.BR error ()
+T}	Thread safety	MT-Safe locale
+T{
+.BR error_at_line ()
+T}	Thread safety	T{
+MT-Unsafe race:error_at_line/error_one_per_line locale
+T}
+.TE
+
+The internal
+.I error_one_per_line
+variable is accessed (without any form of
+synchronization, but since it's an int used once, it should be safe
+enough) and, if this mode is enabled, static variables used to hold
+the last printed file name and line number are accessed and modified
+without synchronization; the update is not atomic and it occurs
+before disabling cancellation, so it can be interrupted after only
+one of the two variables is modified.  After that, it's very much
+like
+.BR error (3).
 .SH CONFORMING TO
 These functions and variables are GNU extensions, and should not be
 used in programs intended to be portable.