https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99355
--- Comment #12 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Additional patch – my need some cleanup & check whether the
other flags agree with the description. However, it should
match the implementation:
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -519,8 +519,13 @@ representation of the translated Fortran code, produced by
@opindex @code{freal-8-real-16}
@cindex options, real kind type promotion
Promote all @code{REAL(KIND=M)} entities to @code{REAL(KIND=N)} entities.
-If @code{REAL(KIND=N)} is unavailable, then an error will be issued.
-All other real kind types are unaffected by this option.
+If @code{REAL(KIND=N)} is unavailable, then an error will be issued;
+the real-4 flags also affect the default real kind, the real-8 flag also
+the double-precision real kind. All other real kind types are
+unaffected by this option. For real literal constants, the promoted
+values are used for the default kinds and a specified kind value is
+promoted to the new value. Note that when using @code{REAL(KIND=KIND(1.0))}
+the literal is first promoted and then the result is promoted again.
These options should be used with care and may not be suitable for your
codes. Areas of possible concern include calls to external procedures,
alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
