Thread: Error converting to same format?

Here's my latest compilation error:

error: invalid conversion from 'void (*)(_DNSServiceRef_t*, DNSServiceFlags, uint32_t, DNSServiceErrorType, char*, char*, char*, void*)' to 'void (*)(_DNSServiceRef_t*, DNSServiceFlags, uint32_t, DNSServiceErrorType, const char*, const char*, const char*, void*)'|

Maybe I'm crazy, but they're the exact same thing, what's the problem?

FlyingIsFun1217

They are not the same note the char* versus const char*

Looks like it took a set of unwary eyes to spot that; thanks

FlyingIsFun1217

Well, it went from understandable to mind(mine)-boggling:

Changed the code, here's what I get now:

error: invalid conversion from 'void (*)(_DNSServiceRef_t*, DNSServiceFlags, uint32_t, DNSServiceErrorType, const char*, const char*, const char*, void*)' to 'void (*)(_DNSServiceRef_t*, DNSServiceFlags, uint32_t, DNSServiceErrorType, const char*, const char*, const char*, void*)'

God I hate trying to work with Bonjour.

FlyingIsFun1217

Ask and your wish shall be granted

Code:

#include "dns_sd.h"
#include <stdio.h>
#include <string.h>

void HandleEvents(DNSServiceRef)
{
    //Placeholder
}

static void MyBrowseCallBack(DNSServiceRef service,
                             DNSServiceFlags flags,
                             uint32_t interfaceIndex,
                             DNSServiceErrorType errorCode,
                             const char * name,
                             const char * type,
                             const char * domain,
                             void * context)
                             {
                                 //#pragma unused(context)
                                 if(errorCode != kDNSServiceErr_NoError)
                                 {
                                     fprintf(stderr, "MyBrowseCallBack returned %d\n", errorCode);
                                 }
                                 else
                                 {
                                     const char *addString = (flags & kDNSServiceFlagsAdd) ? "ADD" : "REMOVE";
                                     const char *moreString = (flags & kDNSServiceFlagsMoreComing) ? "MORE" : "";

                                     printf("%-7s%-5s %d%s.%s%s\n", addString, moreString, interfaceIndex, name, type, domain);
                                 }

                                 if(!(flags & kDNSServiceFlagsMoreComing))
                                 {
                                     fflush(stdout);
                                 }
                             }

static DNSServiceErrorType MyDNSServiceBrowse()
{
    DNSServiceErrorType error;
    DNSServiceRef serviceRef;

    error = DNSServiceBrowse(&serviceRef,
                             0,
                             0,
                             "_touch-remote._tcp",
                             "",
                             MyBrowseCallBack,
                             NULL);

    if(error == kDNSServiceErr_NoError)
    {
        HandleEvents(serviceRef); //Look up HandleEvents function to learn purpose of it
        DNSServiceRefDeallocate(serviceRef);
    }

    return error;
}

int main(int argc, const char * argv[])
{
    DNSServiceErrorType error = MyDNSServiceBrowse();
    if(error)
    {
        fprintf(stderr, "DNSServiceDiscovery returned %d\n", error);
    }
    return 0;
}

The error is being thrown at line 49, the NULL argument of DNSServiceBrowse while setting DNSServiceTypeError error.

Thanks again,

FlyingIsFun1217

Well, it's linking into Apple's DNS-SD library, which is quite complex, so I'll spare you the pain of scrolling through it. It can be found here though, if you'd like to look at it, the only changes being that the initial U/INT* typedefs have been removed because mingw throws errors when trying to compile with them (I added && ! defined(__MINGW32__)).

That's really the only reason I'm having a problem with this, is that it won't compile after throwing that error every time, so to give you something compilable I can't do (that's my exact problem). I have a feeling my only actual issue though is the lack of the type definitions I referenced to removing, in which case I need to figure out how to get mingw to accept them.

Thanks again,

FlyingIsFun1217

My tiny little self-taught brain is starting to lose track of things. What is going on with the typedef? I've never seen one with parameters (?), as if it were defining the void type or something.

And what do you mean by saying that the function needs to be marked with this type (I assume DNSSD_API is a type?). Where?

Maybe there's a concept I'm missing out on in C++ that could be briefly explained/linked to?

Thanks again

Thank you, the perfect reference I was looking for.

I'll review it, hopefully learn something, and dare I say, return with any more problems.

FlyingIsFun1217

Alright, I've read a bit on it, and at least for me, it's a bit of a confusing topic (methods of working at a low assembly level?), but I've added what seems necessary to me to my code:

Code:

static void DNSSD_API MyBrowseCallBack(...)

Now everything compiles fine, but when it comes to linking time, I get two errors:

obj\Release\main.o:main.cpp|| undefined reference to `DNSServiceBrowse@28'
obj\Release\main.o:main.cpp|| undefined reference to `DNSServiceRefDeallocate@4'

This seems odd, as they're in dns_sd.h, which is linked to in my main.cpp. What is it missing? Is this a project setting within the IDE?

Thanks again

Yeah, and that's kind of what I was afraid of. Bonjour provides a .lib library, but I'll have to find some way to use it within gcc, since it's meant for MSVC. Honestly, if MSVC had as simple of a compiler installation, I would be using it right now :/

Thanks