C++ compiler error “was not declared in this scope”

ccompiler-errorsg++

I'm getting a bizarre compiler error when trying to compile a c++ UDP client program.

g++ -o client Udp.cpp ClientMain.c -I. -lpthread

In file included from ClientMain.c:1:0:

Udp.h: In destructor ‘CUdpMsg::~CUdpMsg()’:

Udp.h:103:43: error: ‘free’ was not declared in this scope

Udp.h: In member function ‘void CUdpMsg::Add(in_addr_t, const void*, size_t)’:

Udp.h:109:34: error: ‘malloc’ was not declared in this scope

Udp.h:109:41: error: ‘memcpy’ was not declared in this scope

ClientMain.c: In function ‘int main(int, char**)’:

ClientMain.c:28:57: error: ‘memcpy’ was not declared in this scope

ClientMain.c:29:61: error: ‘printf’ was not declared in this scope

ClientMain.c:30:17: error: ‘stdout’ was not declared in this scope

ClientMain.c:30:23: error: ‘fflush’ was not declared in this scope

ClientMain.c:34:68: error: ‘printf’ was not declared in this scope

ClientMain.c:35:17: error: ‘stdout’ was not declared in this scope

ClientMain.c:35:23: error: ‘fflush’ was not declared in this scope

ClientMain.c:37:30: error: ‘usleep’ was not declared in this scope

I have the following declared at the beginning of my cpp file.

#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <cstdlib> 
#include <string>
#include <stdlib.h>
#include <cstring>

#include <errno.h>

functions like 'memcpy' should be declared in string.h… I have it (and string and cstring) all declared, and I'm still getting these compiler errors. Does anyone have a clue why this is happening? Thanks.

Best Answer

Your Udp.h file also needs to include the needed system headers. Additionally, since you use cstring and cstdlib as your includes, you'll need to qualify all the C-library functions with std:: since they aren't automatically imported into the global namespace by those headers.

Related Solutions

C++ – error when using g++: ‘malloc’ was not declared in this scope

Namespaces and include files are two totally different things. You need to

#include <stdlib.h>

or, equivalently,

#include <cstdlib>

in order to get access to the declarations in that header file.

Your using-declaration

using namespace std;

on the other hand, means that you can use identifiers that are part of the namespace std, i.e. that were declared inside

namespace std {
  /*...*/
}

without prepending std:: each time.

For example, if you include <string>, you can use the data type std::string, but if you also add using namespace std;, you can use that data type simply as string.

Note, however, that malloc is not defined inside any namespace, so in order to use that, you need only to include stdlib.h.

Note For the difference between stdlib.h and cstdlib, see here.

C++ – How do i fix this error “was not declared in this scope”

Simple fix. Move the function definitions above the void father() function

In code

sem_t mutex;
sem_t S;
char buffer[1024];
void error(const char *msg)
{
 perror(msg);
 exit(0);
}

/*void signal_callback_handler()
{
    close(sockfd);

}*/

   void takef(int &sockfd)
{

*
*
*  *Other code*
*
*
*
    testa(sockfd);

*  *Other code*
*
*
*
}


void testa(int &sockfd)
{
*
*
*
*  *Other code*
*
*
*

}

void putf(&sockfd)
{
*
*
*
*  *Other code*
*
*
*
test();
test();
sem_post(&mutex);

}



void father(int &sockfd)
{
    while(1)
    {
        srand(time(NULL));
        int ms= rand() % 2000 + 5000
        send(sockfd, DATA, strlen(DATA), 0);
        usleep(1000*ms);
        takef(sockfd);
        putf(sockfd);
    }

}


int main(int argc, char *argv[])
{
*
*
*
*  *Other code*
*
*
*
father(sockfd);

return 0;

}

Or another alternative, like mentioned below, is to write a function prototype. This is similar to how one would write a prototype for functions in a header file and then define the functions in a .cpp file. A function prototype is a function without a body and lets the compiler know the function exists but is not defined yet.

Here is an example using prototyping

sem_t mutex;
sem_t S;
char buffer[1024];
void error(const char *msg)
{
    perror(msg);
    exit(0);
}
/*void signal_callback_handler()
{
    close(sockfd);

}*/

// Prototypes
void takef(int &sockfd);
void testa(int &sockfd);
void putf(&sockfd);

void father(int &sockfd)
{
    while(1)
    {
        srand(time(NULL));
        int ms= rand() % 2000 + 5000
        send(sockfd, DATA, strlen(DATA), 0);
        usleep(1000*ms);
        takef(sockfd);
        putf(sockfd);
    }

}

void takef(int &sockfd)
{

*
*
*  *Other code*
*
*
*
    testa(sockfd);

*  *Other code*
*
*
*
}


void testa(int &sockfd)
{
*
*
*
*  *Other code*
*
*
*

}

void putf(&sockfd)
{
*
*
*
*  *Other code*
*
*
*
test();
test();
sem_post(&mutex);

}

int main(int argc, char *argv[])
{
*
*
*
*  *Other code*
*
*
*
father(sockfd);

return 0;

}

Best Answer

Related Solutions

C++ – error when using g++: ‘malloc’ was not declared in this scope

C++ – How do i fix this error “was not declared in this scope”

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