Question

I’ve integrated the ZXing QR Code reader library (ZXingWidget) into my iPhone app, but it conflicts with a function from within the CocoaLumberjack logging library that I am also using.

Undefined symbols for architecture i386:
"ExtractFileNameWithoutExtension(char const*, signed char)", referenced from: ...

DDLog.h
NSString *ExtractFileNameWithoutExtension(const char *filePath, BOOL copy);

#define THIS_FILE (ExtractFileNameWithoutExtension(__FILE__, NO))

DDLog.m
NSString *ExtractFileNameWithoutExtension(const char *filePath, BOOL copy) { ...

As I call it in:

DDLogVerbose(@"%@:%@", THIS_FILE, THIS_METHOD);

The cause for this is that whichever Obj-C file contains the headers:

// import QR Code reader APIs
#import "ZXingWidgetController.h"
#import "QRCodeReader.h"

its file extension must be changed from .m to .mm for proper C++ support.

But then I lose my *DDLogVerbose(@”%@:%@”, THIS_FILE, THIS_METHOD);* functionality.

What am I missing here to have these two play nice with each other?

Answer 1

If you’re including C headers that aren’t “C++-ified” into a C++ or Objective C++ file, you need to tell the compiler. Something like

extern "C" {
#include "DDlog.h"
}

in your .mms should work. Alternatively, if DDLog.h is your file, you can do something like

#ifdef __cplusplus
extern "C"
#endif
NSString *ExtractFileNameWithoutExtension(const char *filePath, BOOL copy);

A web search for “extern C” should provide more details/examples.