Re: [libvirt] [PATCHv2] storage_encryption: silence clang warning

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.

From man printf: