Merge pull request #1492 from schveiguy/cycleswitch

Changelog for new cycle detection behavior switches.

changelog/2.072.0_pre.dd

@@ -108,6 +108,8 @@ $(BUGSTITLE Library Changes,
     $(LI $(RELATIVE_LINK2 emplace-inner-class, `std.conv.emplace` no longer allows
     to emplace classes directly nested inside other classes without specifying a
     suitable `outer` pointer))
+    $(LI $(RELATIVE_LINK2 drt-oncycle, New druntime switch `--DRT-oncycle`
+    allows specifying what to do on cycle detection in modules.))
 )
 
 $(BR)$(BIG $(RELATIVE_LINK2 bugfix-list, List of all bug fixes and enhancements in D $(VER).))
@@ -730,6 +732,19 @@ $(BUGSTITLE Library Changes,
                             // now it works as expected
     -------
     )
+
+    $(LI $(LNAME2 drt-oncycle, New druntime switch `--DRT-oncycle` allows
+        specifying what to do on cycle detection in modules.)
+        $(P When module cycles are detected, the default behavior is to print the cycle, and abort execution. However, in many cases, the cycles are not harmful. With the new `--DRT-oncycle` switch, you can effect a different behavior when cycles are detected:)
+        $(DL
+            $(DT `--DRT-oncycle=abort`)
+            $(DD This is the default behavior, and will abort, printing the cycle to `stderr` when the first cycle is detected)
+            $(DT `--DRT-oncycle=print`)
+            $(DD Print all cycles that are detected to `stderr`, but do not halt execution. Order of initialization is arbitrarily chosen based on the order the modules are in the binary)
+            $(DT `--DRT-oncycle=ignore`)
+            $(DD Do not print anything, and do not halt execution. Order of initialization is arbitrarily chosen based on the order the modules are in the binary)
+        )
+    )
 )
 )
 

spec/module.dd

@@ -542,6 +542,22 @@ $(H3 $(LNAME2 order_of_static_ctor, Order of Static Construction))
 	in a runtime exception.
 	)
 
+$(H3 $(LNAME2 override_cycle_abort, Overriding Cycle Detection Abort))
+
+        $(P You can override the cyclic detection behavior using the D Runtime
+        switch `--DRT-oncycle=...` The following behaviors are supported:
+        )
+
+        $(OL
+            $(LI `abort` The default behavior.)
+            $(LI `print` Print all cycles detected, but do not abort execution.
+            Order of static construction is implementation defined, and not
+            guaranteed to be valid.)
+            $(LI `ignore` Do not abort execution or print any cycles. Order of
+            static construction is implementation defined, and not guaranteed
+            to be valid.)
+        )
+
 $(H3 $(LNAME2 order_of_static_ctors, Order of Static Construction within a Module))
 
 	Within a module, the static construction occurs in the lexical