[Mono-bugs] [Bug 28186][Wis] Changed - Doesn't report error CS0177: Out parameter must be assigned before leaving method

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Changed by miguel@ximian.com.

http://bugzilla.ximian.com/show_bug.cgi?id=28186

--- shadow/28186	Thu Jul 25 08:02:10 2002
+++ shadow/28186.tmp.26187	Thu Jul 25 16:46:37 2002
@@ -1,14 +1,14 @@
 Bug#: 28186
 Product: Mono/MCS
 Version: unspecified
-OS: 
+OS: unknown
 OS Details: 
 Status: NEW   
 Resolution: 
-Severity: 
+Severity: Unknown
 Priority: Wishlist
 Component: Misc
 AssignedTo: martin@gnome.org                            
 ReportedBy: martin@gnome.org               
 QAContact: mono-bugs@ximian.com
 TargetMilestone: ---
@@ -23,6 +23,35 @@
 must 
 	be assigned to before control leaves the current method."
 
 -----
 
 This compiled fine for me with MCS, so MCS fails to report that error.
+
+------- Additional Comments From miguel@ximian.com  2002-07-25 16:46 -------
+This bug requires data flow analysis, basically "out" variables should
+be "definitely assigned" every time we return.
+
+I do not know how to implement this yet, i have been struggling with a
+few ideas. 
+
+Guavac did it this way: every variable is tracked in a bit vector, and
+during code forks, the bit vector is duplicated:
+
+if (xxx){
+...
+} else {
+...
+}
+
+Then the bit vectors are merged at this point.  This is used to keep
+track of which variables have been definitely assigned, and which ones
+have not.  But I am not sure how to map our current variables to
+bitvectors.
+
+Then, when *using* a variable (out parameters and locals are the only
+ones considered in definite assignment) we have to check if it is
+definitely assigned.
+
+And we have to check that all out variables are definitely assigned
+when we return.
+