re PR fortran/81344 (Can't disable -ffpe-trap (or not documented))

2019-02-02  Dominique d'Humieres  <dominiq@gcc.gnu.org>

	PR fortran/81344
	* invoke.texi: Document the behavior of repeated -ffpe-trap
	and -ffpe-summary.

From-SVN: r268480

gcc/fortran/ChangeLog

+2019-02-02  Dominique d'Humieres  <dominiq@gcc.gnu.org>
+
+	PR fortran/81344
+	* invoke.texi: Document the behavior of repeated -ffpe-trap
+	and -ffpe-summary.
+
 2019-02-02  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/88298

gcc/fortran/invoke.texi

@@ -1203,6 +1203,12 @@ The first three exceptions (@samp{invalid}, @samp{zero}, and
 has provisions for dealing with these exceptions, enabling traps for
 these three exceptions is probably a good idea.
 
+If the option is used more than once in the command line, the lists will
+be joined: '@code{ffpe-trap=}@var{list1} @code{ffpe-trap=}@var{list2}'
+is equivalent to @code{ffpe-trap=}@var{list1,list2}.
+
+Note that once enabled an exception cannot be disabled (no negative form).
+
 Many, if not most, floating point operations incur loss of precision
 due to rounding, and hence the @code{ffpe-trap=inexact} is likely to
 be uninteresting in practice.
@@ -1218,6 +1224,9 @@ of the following exceptions: @samp{invalid}, @samp{zero}, @samp{overflow},
 @samp{underflow}, @samp{inexact} and @samp{denormal}. (See
 @option{-ffpe-trap} for a description of the exceptions.)
 
+If the option is used more than once in the command line, only the
+last one will be used.
+
 By default, a summary for all exceptions but @samp{inexact} is shown.
 
 @item -fno-backtrace