c - initialization makes integer from pointer without a cast and 2 more compiler errors

Question

so I'm getting this warning:

initialization makes integer from pointer without a cast

in the following piece of code:

void receive(u_char *args, const struct pcap_pkthdr *pkthdr, const u_char *buffer)

{

const int one = 1;

int LEN = args;      /* THIS IS THE LINE */

struct ipheader *ip;

struct tcpheader *tcp;

and to be honest little newbie me is not sure what to do as almost all searches return makes pointer from integer.

I'm also getting these compiler messages:

/tmp/cci6u7NH.o: In function `main':
ChannelBunny.c:(.text+0x448): undefined reference to `pthread_create'
ChannelBunny.c:(.text+0x4b7): undefined reference to `pthread_join'
/tmp/cci6u7NH.o: In function `receive':
ChannelBunny.c:(.text+0xcb6): undefined reference to `nthol'
ChannelBunny.c:(.text+0xcdf): undefined reference to `nthol'
collect2: ld returned 1 exit status

got rid of a similar pcap problem by using -l pcap but that didn't work for the other two. It just returned:

gcc: pthread: No such file or directory
gcc: nthol: No such file or director

I'm guessing I have to download something? or is there another command I have to use. (I'm using Backtrack5 if that's of any use to you).

Solution 1

You should do

int LEN = *args;

args is a pointer, *args is the value pointed by it. Also, you shouldn't put a u_char into an int.

For nthol: http://msdn.microsoft.com/en-us/library/windows/desktop/ms740069(v=vs.85).aspx

Solution 2

You can use atoi() function to convert char* to int.

About the link error about pthread, try put -lpthread on your compile command

Comments

[Tim Post]

I'm speaking as a C programmer here, not a moderator. Please do not recommend the use of atoi(), strtol() is much, much safer.

[youjustreadthis]

Never used atoi() before, but there is a pcap_loop function further down that I didn't include here which I believe is expecting a char*. wouldn't atoi() conflict with that? -lpthread worked brilliantly btw :) @TimPost how would that look in my example?

[Tim Post]

@youjustreadthis Just LEN = strtol(args, NULL, 0), the spec is quite informative. But I'm not sure why args is u_char ?

[mask8]

@youjustreadthis what do you expect args to be? @TimPost I agree. if you are not sure what you are passing to atoi

[mask8]

@youjustreadthis oh, so you are receiving a pointer at args, which you actually pass to pcap_loop() what are you passing in the pcap_loop()? it's up to what you expect to have in LEN

[youjustreadthis]

@TimPost well i'm going by an example program I found so I could try to put together a 3 way tcp connection. And that is how it looked like. I was alsu under the impression that (pcap_loop(pd, -1, receive, (u_char *) &dl_len) < 0) requires a u_char in the recieve function. Got it to compile now so with any (lots considering my skills haha) luck it'll work, but we'll see.