Unused parameter warning

Question

I am getting "unused parameter 'testString'" warning from following code. But I am using testString to log. So how come it is unused ?

- (void)getString:(NSString *)testString {
          ICELogInfo(@"%@", testString);
}

ICELogInfo is a macro for NSLog.

#define ICELogInfo(fmt, ...) LOG_FORMAT(fmt, @"INFO", ##__VA_ARGS__)
#define LOG_FORMAT(fmt, lvl, ...) LOG_FORMAT_NO_LOCATION(fmt, lvl, ##__VA_ARGS__)
#define LOG_FORMAT_NO_LOCATION(fmt, lvl, ...) NSLog((@"%@ " fmt), lvl, ##__VA_ARGS__)

What I am doing wrong ?

It will log " INFO <--testString-->". Logging part is working fine. I don't have any problem with the output. Just that warning. — AAV, Jul 09 '13 at 18:58
Could it be that ICELogInfo is defined as "nothing" in the non-DEBUG case? — Martin R, Jul 09 '13 at 21:09
@AmitVyawahare: It could be that the above definition is only used in the `#ifdef DEBUG` case and otherwise ICELogInfo is defined as an empty macro. — Martin R, Jul 10 '13 at 16:19

gsach · Accepted Answer · 2013-07-09T19:30:37.527

6

You aren't doing something wrong. This is a common problem when using macros.

As a workaround if you want to get rid of the warning, you can use this code:

- (void)getString:(NSSTring*) __unused testString {
          ICELogInfo(@"%@", testString);
}

edited Jul 09 '13 at 19:30

answered Jul 09 '13 at 19:02

gsach

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thank you and this is a good work around but I am looking for why ? – AAV Jul 09 '13 at 19:07

score 2 · Answer 2 · answered Jul 09 '13 at 19:05

2

I've run into the same "problem" before. Solved it by using the unused flag as e.g.

- (void)getString:(NSString *)testString {
    ICELogInfo(@"%@", testString);
    #pragma unused (testString)
}

answered Jul 09 '13 at 19:05

Groot

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thank you and this is a good work around as well but I am looking for why ? – AAV Jul 09 '13 at 19:08

score 1 · Answer 3 · answered Jul 13 '13 at 19:51

What version of Xcode are you using? This looks like a lambda capture bug in LLVM from over a year ago now:

[LLVMbugs] [Bug 12153] New: Incorrect warning about unused parameter when using capturing variadic parameter in lambda

as the VA_ARGS in those macros can be expected to work out to the same problem described in that bug report; but it should be resolved in recent Xcodes. Definitely is in Xcode 5 DP 3 that I'm running right now, your code gives me no warnings.

Unused parameter warning

3 Answers3