C++ string question

[Mark Rivers via Core-talk <core-talk@aps.anl.gov>]

I have defined the following macro to print an error message:

 

#define ERR_ARGS(fmt,...) asynPrint(mSet->getUser(), ASYN_TRACE_ERROR, \

    "Param[%s]::%s: "fmt"\n", mAsynName.c_str(), functionName, __VA_ARGS__);

 

 

I call it like this:

 

        if(status) {

            ERR_ARGS("[param=%s] failed to create param", mAsynName.c_str());

            throw std::runtime_error(mAsynName);

        }

 

So the fmt macro argument is a constant string, which is concatenated with the other constant strings in this _expression_:     "Param[%s]::%s: "fmt"\n"

 

This compiles fine with gcc 4.8.5 and Visual Studio 2015.

 

However, on gcc 7.3.0 (Ubuntu 18) I get the following error:

 

../GenICamFeature.cpp: In constructor ‘GenICamFeature::GenICamFeature(GenICamFeatureSet*, const string&, asynParamType, int, const string&, GCFeatureType_t)’:

../GenICamFeature.cpp:15:25: error: unable to find string literal operator ‘operator""fmt’ with ‘const char [17]’, ‘long unsigned int’ arguments

     "Param[%s]::%s: "fmt"\n", mAsynName.c_str(), functionName, __VA_ARGS__);

                         ^

/corvette/home/epics/devel/asyn-4-35/include/asynDriver.h:272:66: note: in definition of macro ‘asynPrint’

     ? pasynTrace->printSource(pasynUser,reason,__FILE__,__LINE__,format) \

                                                                  ^~~~~~

../GenICamFeature.cpp:80:13: note: in expansion of macro ‘ERR_ARGS’

             ERR_ARGS("[param=%s] failed to create param", mAsynName.c_str());

             ^~~~~~~~

 

Any ideas why I am getting the error and how to eliminate it?

 

Thanks,

Mark