Passing a FLOAT to a function with e.g. a BYTE signature

[Karl1155]

I m wondering why this code compiles without a warning/error. Trying the same with VO results in: "Possibly dangerous automatic conversion ... 51458"

btw. none of the X# compiler options are set

FUNCTION Start( ) AS VOID
LOCAL f := -1343.345 AS FLOAT  // "AS DOUBLE" throws an compile error

TestFloat ( f ) 

f := 12345673.89

TestFloat ( f ) 

RETURN


FUNCTION TestFloat ( n AS BYTE ) AS INT  
	? n   // shows 193 and 73
	RETURN 0

Karl-Heinz

[RobertvanderHulst]

I am not sure what's happening here. Therefore I don't know if I have to call this a bug or an enhancement.

[cpyrgas]

Hmmm, indeed something seems to have gone wrong lately regarding conversions. First of all, when /vo7 is enabled the following does not report errors or even warnings, even if /vo4 (implicit signed/unsigned convertions) is disabled:

// /vo7+  /vo4-
FUNCTION Start() AS VOID
LOCAL d := 0 AS DWORD
LOCAL i := 0 AS INT
d := i
i := d

I think in this case there should be an error, since /vo4 is disabled. If /vo4 is enabled, then correctly there's no error, but the problem is there's not a warning either, which I think was being reported in older compiler versions.

For other numeric data types the behavior seems inconsistent again, and most importantly it seems that again both /vo4 and /vo7 have the same effect on the compiler behavior in those conversions:

LOCAL r AS REAL4
LOCAL f AS FLOAT
LOCAL i AS INT
LOCAL d AS DWORD
LOCAL b AS BYTE

r := i // no warning/error, correct
f := i // no warning/error, correct
r := d // no warning/error, correct
f := b // no warning/error, correct

i := r // correct error XS0266: Cannot implicitly convert type 'real4' to 'int' when no options used, but no warning with /vo4 or /vo7
i := f // no error or warning at all, wrong!

b := r // error with no options, no warning with either /vo4+ or /vo7+
b := f // no error or warning at all, wrong!
b := i // error with no options, no warning with either /vo4+ or /vo7+
b := d // error with no options, no warning with either /vo4+ or /vo7+

So there's definitely a bug here, but please let's give this high priority, because it's a very "fragile" area in the compiler/runtime, right now it seems it's not causing problems to applications, it's only not preventing programmer errors as it should. Would be very nice to fix of course, but let's make absolutely sure that we do not break anything that does work correctly right now.

[RobertvanderHulst]

The problem is not in the compiler but in the Runtime.
The conversion operators in the Float class (and also in the Currency class) convert without overflow checking.
I will add this to both numeric types.

[cpyrgas]

Robert, this now makes the original code throw a runtime exception, which is indeed a lot better than giving "random" results, but the original problem remains, shouldn't the compiler report an error or warning on this code? Especially since no vo* compiler options are being used and since it does report an error with REAL8 instead of FLOAT.

Similarly the cases I reported in my previous notes are not affected by this change. Or did I miss a compilee change, too?

[RobertvanderHulst]

The compiler can't report an error because the code will sometimes run (when the values are in the correct range) and sometimes will fail.

[RobertvanderHulst]

Similarly the cases I reported in my previous notes are not affected by this change. Or did I miss a compilee change, too?

I did not check that code. Will do that asap.