On Mon, May 10, 2010 at 02:12:29PM -0600, Eric Blake wrote:
> On 05/10/2010 01:02 PM, Jim Meyering wrote:
> > Eric Blake wrote:
> >> For printf("%*s",foo,bar), clang complains if foo is not int:
> >>
> >> warning: field width should have type 'int', but argument has
> >> type 'unsigned int' [-Wformat]
> >>
> >> virStorageEncryptionSecretFormat(virBufferPtr buf,
> >> virStorageEncryptionSecretPtr secret,
> >> - unsigned int indent)
> >> + int indent)
> >
> > "unsigned int" sounds like the right type to me, since
> > "indent" never goes negative. And using the unsigned type
> > seems to be in line with policy in HACKING:
> >
> > If a variable is counting something, be sure to declare it with an
> > unsigned type.
>
> But printf("%*s", indent, string) would indeed behave differently if
> indent goes negative (if signed) or larger than INT_MAX (if unsigned),
> so clang's warning is realistic, and worth silencing in our quest to get
> a clean clang build. About the only other thing I could think of to do
> that would avoid confusion and also to avoid casts is to keep the public
> interface with unsigned int, then add an intermediate helper variable:
>
> int real_indent = indent;
>
> and use real_indent in the printf call, but that seems like overkill.
>
> >
> > Of course, avoiding casts is good, too, but IMHO, not if
> > it makes us obfuscate (even ever so slightly) the types we use.
>
> Well, the real point of this patch was to silence a compiler warning
> (not that we'd ever planning on passing an indent > 2G). Given Dave's
> ACK, I went ahead and applied v2 as proposed, even if it does slightly
> obfuscate the usage.
It's valid to pass a negative value, so int is the correct type. My
bad for using unsigned int in the first place.
>From man printf:
A negative field width is taken as a '-' flag followed by a positive
field width.
Dave
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list