------- Comment #64 from baldrick at free dot fr 2008-03-30 16:02 ------- Subject: Re: VRP fails to eliminate range checks in Ada code
> > But there are no checks on the array access. It looks like the f-e > > doesn't generate them in the first place (as opposed to fold or gigi > > making a mistake). > > This is as documented in the GNAT manual, section 3.2.4 Validity Checking. > You need to pass -gnatVs to have them. Consider the following test case: procedure Overflow (X : Positive) return Integer is A : array (Positive) of Integer; pragma Import (Ada, A); begin A (X) := X; end; (for which no checks are generated). In the user guide GNAT GPL User's Guide The GNAT Ada Compiler GNAT GPL Edition, Version 2007 Document revision level 1.422 Date: 2007/03/30 03:28:29 in section 3.2.4 it says: In GNAT, the result of such an evaluation in normal default mode is to either use the value unmodified, or to raise Constraint_Error in those cases where use of the unmodified value would cause erroneous execution. The cases where unmodified values might lead to erroneous execution are case statements (where a wild jump might result from an invalid value), and subscripts on the left hand side (where memory corruption could occur as a result of an invalid value). This testcase is a clear example of erroneous execution, being of the type explicitly mentioned. So according to section 3.2.4 Constraint_Error should be raised "in normal default mode". Yet this is not the case. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30911
