Thread: Problem with library

Originally Posted by QQemka

Im sure i included pcap.h, and set something in linker and compiler. When i will be back home in 1-2 hours i will post it with some screens

Post the Full Compiler Build Log; after you turn on logging.
From FAQ-Compiling (errors) - CodeBlocks

Q: How do I troubleshoot a compiler problem?

A: I would start by turning on full Compiler logging.

This is done by selecting the "Full command line" option Under menu "Settings" -> "Compiler and Debugger" -> Global compiler settings -> [the compiler you use] -> "Other Setting" tab, "Compiler logging".

This option will make Code::Blocks output the exact commands it uses to compile your code.

Things to remember:

You should review all the commands and their options;
If you have compiled your app before, do a re-build (or clean before build) to see all compiling / linking steps;
If you don't know what an option or a command does please read the documentation for the compiler/linker you're using;
Look for missing commands;
For every source file (.cpp; .c; .d; etc) in your project, you must have at least one command in the log. This command must produce an object file (file extension .o if using gcc/g++ and .obj if using Visual Studio);
Every object file should be linked in the final executable, if not there are undefined symbols errors;
Remember the file extension matters: *.c is compiled as C file, *.cpp is compiled as C++ file.

Tim S.

I have everything set good, i think i have chosen wrong packet library... every tutorial for winpcap is in C, not in c++ do you know any other one? I need only to write a simple sniffer

It may be problem that im using codeblocks instead of visual studio whatever it is?

Originally Posted by QQemka

I have everything set good, ...

If you want a second opinion; once more, I suggest posting the full build log.

Tim S.

This is the tutorial i am using Programming with pcap

The source code i am trying to compile is one of first

Code:

#include <stdio.h> 
#include <pcap.h>
int main(int argc, char *argv[])     { 
char *dev, errbuf[PCAP_ERRBUF_SIZE]; 
dev = pcap_lookupdev(errbuf);
if (dev == NULL) { 
fprintf(stderr, "Couldn't find default device: %s\n", errbuf);
return(2);
}
printf("Device: %s\n", dev);
return(0);
}

Build log:
-------------- Build: Debug in qqqqqqq ---------------

mingw32-g++.exe -L"C:\Documents and Settings\QQemka\Pulpit\WpdPack\Lib" -o bin\Debug\qqqqqqq.exe obj\Debug\main.o
obj\Debug\main.o: In function `main':
C:/Documents and Settings/QQemka/Pulpit/qqqqqqq/main.cpp:8: undefined reference to `pcap_lookupdev
'
collect2: ld returned 1 exit status
Process terminated with status 1 (0 minutes, 0 seconds)
1 errors, 0 warnings


Build messages:
obj\Debug\main.o||In function `main':|
C:\Documents and Settings\QQemka\Pulpit\qqqqqqq\main.cpp|8|undefine d reference to `pcap_lookupdev|
||=== Build finished: 1 errors, 0 warnings ===|


In settings>search directories>compiler path is "C:\Documents and Settings\QQemka\Pulpit\WpdPack\Include"
settings>search directories>Linker "C:\Documents and Settings\QQemka\Pulpit\WpdPack\Lib"



I have just found out that i got some example files. I cannot compile them, mass errors. But they are all C not cpp, so maybe the library wont work with cpp??

To link to a library you actually need to link to a library!

This means you need a library name in the command; NOT just a path to a library.

Normally the command will have -lname where "name" is replaced with the library name.

In using Code::Blocks with GCC if the library file-name is libname.a you would enter only name without the leading lib or the trailing .a in the list of library names.

I am guessing the correct library file-name is "libwpcap.a" so try wpcap in the library list.
Under "Project" -> "Build Options"
Tab: Linker Settings
Box: Link Libraries

My full build log follows

Code:

mingw32-gcc.exe -Wall  -g  -Wno-unused-but-set-variable -Wno-deprecated-declarations -Wno-unused-variable -Wno-sign-compare -Wno-unused-parameter -Wno-attributes -Winvalid-pch   -IC:\Users\stahta01\Downloads\WpdPack_4_1_2\WpdPack\Include -IH:\SourceCode\Projects\TestProjects\testpcap -c H:\SourceCode\Projects\TestProjects\testpcap\main.c -o obj\Debug\main.o
mingw32-g++.exe -LC:\Users\stahta01\Downloads\WpdPack_4_1_2\WpdPack\Lib  -o bin\Debug\testpcap.exe obj\Debug\main.o    -lwpcap

The options "-Wno-unused-but-set-variable -Wno-deprecated-declarations -Wno-unused-variable -Wno-sign-compare -Wno-unused-parameter -Wno-attributes -Winvalid-pch" are me testing some other items and can be ignored.

Tim S.

Libraries in Windows tend to end with .lib, not .a.
Regardless, the documentation for pcap should say what file you must link against. That's the filename you input to the compiler.

Originally Posted by Elysia

Libraries in Windows tend to end with .lib, not .a.
Regardless, the documentation for pcap should say what file you must link against. That's the filename you input to the compiler.

Microsoft Visual Studio Libraries and Borland Libraries tend to end with .lib file extension.
MinGW GCC Libraries tend to end with .a file extension.

Tim S.