Conversion of long type to int type
in [C++]
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From: Joseph Bentley on 8 Feb 2010 11:07 This code produces a warning regarding "conversion of long type to int type". .... void funk(int); .... long whatever; .... funk(whatever); // warning here .... Of course, I know that I should avoid these situations when I can, like making funk()'s argument a long. But sometimes funk() is not your function, and you must live with the int argument. So my question is, should I suppress the warning, or is there some cast I don't know about to disguise the problem, some another approach, or forget about it? Thanks, Joe -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Ulrich Eckhardt on 9 Feb 2010 01:43 Joseph Bentley wrote: > This code produces a warning regarding "conversion of long type to int > type". > ... > void funk(int); > ... > long whatever; > ... > funk(whatever); // warning here > ... > > Of course, I know that I should avoid these situations when I can, > like making funk()'s argument a long. But sometimes funk() is not > your function, and you must live with the int argument. Well, you could also change 'whatever' to an int. > So my question is, should I suppress the warning, or is there some > cast I don't know about to disguise the problem, some another approach, > or forget about it? IMHO there are three solutions: 1. Ignore the warning for now, after all it is just a warning. 2. Add a runtime-checked conversion which checks that the conversion is lossless or signals the error. 3. Add an explicit conversion (static_cast) if you know that the long's range doesn't exceed the int's, possibly paired with an assertion that it works without losing any bits. Uli -- Sator Laser GmbH Geschäftsführer: Thorsten Föcking, Amtsgericht Hamburg HR B62 932 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Johannes Schaub (litb) on 9 Feb 2010 01:43 Joseph Bentley wrote: > This code produces a warning regarding "conversion of long type to int > type". > ... > void funk(int); > ... > long whatever; > ... > funk(whatever); // warning here > ... > > Of course, I know that I should avoid these situations when I can, > like making funk()'s argument a long. But sometimes funk() is not > your function, and you must live with the int argument. So my > question is, should I suppress the warning, or is there some cast I > don't know about to disguise the problem, some another approach, or > forget about it? > I would use a static_cast: f(static_cast<int>(whatever)); -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Manan on 9 Feb 2010 01:40 On Feb 8, 10:07 pm, Joseph Bentley <joe.foxho...(a)gmail.com> wrote: > This code produces a warning regarding "conversion of long type to int > type". > ... > void funk(int); > ... > long whatever; > ... > funk(whatever); // warning here > ... > > Of course, I know that I should avoid these situations when I can, > like making funk()'s argument a long. But sometimes funk() is not > your function, and you must live with the int argument. So my > question is, should I suppress the warning, or is there some cast I > don't know about to disguise the problem, some another approach, or > forget about it? { quoted thanks and banner removed -mod } You can use funk(static_cast<int>(whatever)) -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Francis Glassborow on 9 Feb 2010 01:43
Joseph Bentley wrote: > This code produces a warning regarding "conversion of long type to int > type". > ... > void funk(int); > ... > long whatever; > ... > funk(whatever); // warning here > ... > > Of course, I know that I should avoid these situations when I can, > like making funk()'s argument a long. But sometimes funk() is not > your function, and you must live with the int argument. So my > question is, should I suppress the warning, or is there some cast I > don't know about to disguise the problem, some another approach, or > forget about it? > > Thanks, > Joe > You might try producing a checking overload of funk to catch cases where whatever is out of the int range. void funk(long value){ if (value > INT_MAX || value < INT_MIN) throw range_error; return funk( static_cast<int> value ); } And that return is fine, the standard is carefully crafgted to allow return of void in cases like this one. -- [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |