doc: improve -fsanitize=undefined description

gcc/ChangeLog:
	* doc/invoke.texi: Add link to UndefinedBehaviorSanitizer
	documentation, mention UBSAN_OPTIONS, similar to what is done
	for AddressSanitizer.

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8b3ebcfbc4fc22bf325556c4dfdca708fa9ffa3f..c4c653292474db1c7e0b30a8b7279cb53dfde6ad 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -15247,7 +15247,8 @@ The option cannot be combined with @option{-fsanitize=thread}.
 @opindex fsanitize=undefined
 Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.
 Various computations are instrumented to detect undefined behavior
-at runtime.  Current suboptions are:
+at runtime.  See @uref{https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html} for more details.   The run-time behavior can be influenced using the
+@env{UBSAN_OPTIONS} environment variable.  Current suboptions are:
 
 @table @gcctabopt