CODEWITHSUNDEEP
c++installationlibraries
AvinashK
AvinashK

Reputation: 3423

install a library so that c++ compiler can directly access it

I installed libmcrypt on my system by using the following commands:-

avinash@ak-pc:~/Documents/network_lab/tut7$ cd libmcrypt-2.5.8
avinash@ak-pc:~/Documents/network_lab/tut7/libmcrypt-2.5.8$ ./configure --prefix=/usr --disable-posix-threads
avinash@ak-pc:~/Documents/network_lab/tut7/libmcrypt-2.5.8$ make
avinash@ak-pc:~/Documents/network_lab/tut7/libmcrypt-2.5.8$ sudo make install

As a result headers went to /usr/include and the libraries to /usr/lib. Now, when I include < mcrypt.h> into a .cpp file and use functions provided by libmcrypt, the compiler announces

/tmp/ccCot4nH.o: In function `main':
q3.cpp:(.text+0x64): undefined reference to `mcrypt_module_open'
q3.cpp:(.text+0xb9): undefined reference to `mcrypt_generic_init'
q3.cpp:(.text+0xd6): undefined reference to `mcrypt_generic'
q3.cpp:(.text+0x110): undefined reference to `mdecrypt_generic'
q3.cpp:(.text+0x13a): undefined reference to `mcrypt_generic_deinit'
q3.cpp:(.text+0x147): undefined reference to `mcrypt_module_close'
collect2: ld returned 1 exit status

Can anybody tell me where the problem is? Was there something wrong with the installation procedure?

Upvotes: 0

Views: 641

Answers (1)

Delan Azabani
Delan Azabani

Reputation: 81404

Including the header files of a library only provides declarations so that the compiler is aware of function signatures and global variable types, but you also need to indicate to the linker the library your program is to be dynamically linked with.

With most compilers, use the -l flag followed by the library's name, without the lib prefix. For example, your linking command may look something like this:

g++ -o myprogram obj1.o obj2.o ... obj.o -lmcrypt

Upvotes: 2

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