Setting a flag in compiler for NSLog not to show

Question

Is there any particular flag which can be set to not display NSLog output in either debug or release?

Thanks.

Answer 1

One option might be to use a macro as a replacement for NSLog (if its easy for you to change things at this point). I like the prefix header file these guys use:

http://www.cimgf.com/2010/05/02/my-current-prefix-pch-file/

Basically their logging function is:

#ifdef DEBUG
  #define DLog(...) NSLog(@"%s %@", __PRETTY_FUNCTION__, [NSString stringWithFormat:__VA_ARGS__])
#else
  #define DLog(...) do { } while (0)
#endif

So if you are not in a DEBUG build, the logging macro becomes a no-op.

Answer 2

Generally, people write their own macro -- something like DebugLog -- for logs to be "compiled out":

#undef DebugLog
#ifdef DEBUG_MODE
#define DebugLog( s, ... ) NSLog( @"%@", [NSString stringWithFormat:(s), ##__VA_ARGS] )
#else
#define DebugLog( s, ... )
#endif

Answer 3

Adding this b/c none of the answers seem to address warnings you may have (depending on project settings) with some of these approaches.

This is the only way I could find to suppress NSLog without getting any warnings. Otherwise I get a ton with the settings we use (warn on unused variables).

#undef NSLog

#define NSLog(fmt, ...) if (0) { printf("%s", [[NSString stringWithFormat:fmt, ##__VA_ARGS__] UTF8String]); }

Then all you need to do is put that in whatever pch file you use for your release builds or wherever you want to suppress the logs.

Credit to @Hot Licks for the example of how to make the variable "used".

Answer 4

Default flag with a new Xcode project is DEBUG for Debug and none for Release. So you will hide NSLog in Release this way:

#ifndef DEBUG
#   define NSLog(...)
#   define NSLogv(...)
#endif

Or if you want pretty custom logs as well (not using #ifdef here because no simple #elifdef):

#if DEBUG
#   define NSLog(format, ...) NSLog((@"%s " format), __PRETTY_FUNCTION__, ##__VA_ARGS__)
#   define NSLogv(format, ...) NSLog(@"%s %@", __PRETTY_FUNCTION__, [[NSString alloc] initWithFormat:format arguments:__VA_ARGS__])
#elif ADHOC
    // default logs
#else// Release
#   define NSLog(...)
#   define NSLogv(...)
#endif

And if you want to override those macros and still log something sometimes, you can use:

(NSLog)(@"This log is always visible!");

Now, how to hide those as well? It would require you to #define NSLog NoLog and define NoLog as an extern function with an empty implementation like void NoLog(NSString *format, ...) {}. But it could be cleaner to avoid using (NSLog) altogether and instead use a function with a LogLevel enum:

typedef NS_ENUM(NSUInteger, LogLevel) {
    LogLevelRelease,
    LogLevelAdHoc,
    LogLevelDeveloper,
};

void CustomLog(LogLevel level, NSString *format, ...) {
#if !DEBUG
    if (LogLevel == LogLevelDeveloper)
        return;
#if !ADHOC
    if (LogLevel == LogLevelAdHoc)
        return;
#endif
#endif
    va_list ap;
    va_start (ap, format);
    NSLogv(format, ap);
    va_end (ap);
}

The drawback of this CustomLog is that arguments get always evaluated, even in Release. So an optimal solution is multiple macros:

#define NSLog(format, ...) NSLog((@"%s " format), __PRETTY_FUNCTION__, ##__VA_ARGS__)
#if DEBUG
#   define DebugLog(...) NSLog(__VA_ARGS__)
#   define AdHocLog(...) NSLog(__VA_ARGS__)
#   define ReleaseLog(...) NSLog(__VA_ARGS__)
#elif ADHOC
#   define DebugLog(...)
#   define AdHocLog(...) NSLog(__VA_ARGS__)
#   define ReleaseLog(...) NSLog(__VA_ARGS__)
#else// Release
#   define NSLogv(...)
#   define DebugLog(...)
#   define AdHocLog(...)
#   define ReleaseLog(...) NSLog(__VA_ARGS__)
#endif

Answer 5

check for Debug mode using this macro

#ifdef DEBUG
//NSLog(@"XYZ");
#endif

Above NSLog will not get printed in Release mode

Answer 6

You can define a macro in the precompiled header (.pch) to disable NSLog:

#ifdef RELEASE
#   define NSLog(...)
#endif

This disables NSLog in release builds.