如何摆脱这些警告？

Question

This is really several questions, but anyway...

I'm working with a big project in XCode, relatively recently ported from MetroWorks (Yes, really) and there's a bunch of warnings that I want to get rid of. Every so often an IMPORTANT warning comes up, but I never look at them because there's too many garbage ones. So, if I can either figure out how to get XCode to stop giving the warning, or actually fix the problem, that would be great. Here are the warnings:

• It claims that <map.h> is antiquated. However, when I replace it with <map> my files don't compile. Evidently, there's something in map.h that isn't in map...
• this decimal constant is unsigned only in ISO C90
  This is a large number being compared to an unsigned long. I have even cast it, with no effect.

• enumeral mismatch in conditional expression: <anonymous enum> vs <anonymous enum>
  This appears to be from a ?: operator. Possibly that the then and else branches don't evaluate to the same type? Except that in at least one case, it's (matchVp == NULL ? noErr : dupFNErr)

  And since those are both of type OSErr, which is mac defined... I'm not sure what's up. It also seems to come up when I have other pairs of mac constants...

• multi-character character constant

  This one is obvious. The problem is that I actually NEED multi-character constants...

• -fwritable-strings not compatible with literal CF/NSString

  I unchecked the "Strings are Read-Only" box in both the project and target settings... and it seems to have had no effect...

Answer 1

Items in <map.h> are in the global namespace while items in <map> are in the std namespace. Most likely you were just referring directly to the global versions and when you switched to <map> you were no longer seeing them because they moved to std:: . In source files add a using namespace std to move on quickly. In headers you'll need to qualify uses of map-related items with std:: .

I think you'll need to qualify the literal constant value with a trailing UL so it knows the correct type of the literal.

Most likely the enums are in two separate OS defined anonymous enums. You can static_cast them to quiet the warning.

No idea on the multi-byte chars.

Can you disable -fwritable-strings? Can you refactor the code that needs to modify constant strings?

Answer 2

"multi-character character constant"
This one is obvious. The problem is that I actually NEED multi-character constants...

Compile with -Wno-multichar -- add it to Other Warning Flags, and leave the Four Character Literals warning switched off.

Of course, whether this legacy code's multi-character character constants actually mean the same thing as they did under Metrowerks probably on a different architecture... is an open question.

Answer 3

该十进制常数写为3111222333UL吗？

Answer 4

I discovered that at least as of Xcode 3.2.4 you can make the warning go away by using a number of characters in the constant that is the correct length for the type.

For example I had a constant that was only 3 chars long 'TT2' and it was giving me the multi-character character constant error. Adding 0's to the constant made the errors go away, like so: '\\0TT2'.