Here's also an update on the docs to explicitly mention behavior
on overflow.
Maybe this will reach another 0.05% of users...
OK for trunk?
Best regards
Thomas
gcc/fortran/ChangeLog:
* gfortran.texi: Mention behavior on overflow.
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi
index c483e13686d..93c66b18938 100644
--- a/gcc/fortran/gfortran.texi
+++ b/gcc/fortran/gfortran.texi
@@ -820,6 +820,7 @@ might in some way or another become visible to the programmer.
* File operations on symbolic links::
* File format of unformatted sequential files::
* Asynchronous I/O::
+* Behavior on integer overflow::o
@end menu
@@ -1160,6 +1161,23 @@ sytems, such as Linux, it is necessary to specify @option{-pthread},
@c Maybe this chapter should be merged with the 'Standards' section,
@c whenever that is written :-)
+@node Behavior on integer overflow
+@section Behavior on integer overflow
+@cindex integer overflow
+@cindex overflow handling
+
+Integer overflow is prohibited by the Fortran standard. The behavior
+of gfortran on integer overflow is undefined by default. Traditional
+code, like linear congruential pseudo-random number generators in old
+programs that rely on specific, non-standard behavior may generate
+unexpected results. The @option{-fsanitize=undefined} option can be
+used to detect such code at runtime.
+
+It is recommended to use the intrinsic subroutine @code{RANDOM_NUMBER}
+for random number generators or, if the old behavior is desired, to
+use the @option{-fwrapv} option. Note that this option can impact
+performance.
+
@node Extensions
@chapter Extensions
@cindex extensions
