How do i configure g++ to look into particular directory to search library fles?

sadhup · 05-02-2012, 12:51 AM

Hi.. I dont have permission to install on the disk. My program needs to link to mysql DB. I copied the Mysql.h and rest headerrs to local folder and ran the program. While executing, the program throws an error sayin

./a.out: error while loading shared libraries: libmysqlclient.so.16: cannot open shared object file: No such file or directory.
I tried setting the LD_LIBRARY_PATH variable, but dint help. please help me how to go about it.
thanks in advance.

sag47 · 05-02-2012, 01:22 AM

g++ man page or the gcc docs.

Code:

-llibrary
-l library
    Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX compliance and is not recommended.)

    It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz bar.o searches library z after file foo.o but before bar.o. If bar.o refers to functions in z, those functions may not be loaded.

    The linker searches a standard list of directories for the library, which is actually a file named liblibrary.a. The linker then uses this file as if it had been specified precisely by name.

    The directories searched include several standard system directories plus any that you specify with -L.

    Normally the files found this way are library files---archive files whose members are object files. The linker handles an archive file by scanning through it for members which define symbols that have so far been referenced but not defined. But if the file that is found is an ordinary object file, it is linked in the usual fashion. The only difference between using an -l option and specifying a file name is that -l surrounds library with lib and .a and searches several directories.

Code:

-Ldir
    Add directory dir to the list of directories to be searched for -l.

So I would say

Code:

g++ -L/path/to/library -lmysqlclient ...

sadhup · 05-02-2012, 01:29 AM

I tried but is still throwing the same error. I also tried setting the environmental variable LIBRARY_PATH.

Thanks

btmiller · 05-02-2012, 01:38 AM

The environment variable is LD_LIBRARY_PATH. ld is the dynamic linkers, which resolves libraries at runtime whereas the compiler only needs them to link the final executable. You can compile an executable statically (with the -static flag) assuming all required libraries exist statically on the disk (as .a files, not .so files). This was, the program will have no external library dependencies at a cost of a (potentially much) larger binary.

sadhup · 05-02-2012, 02:01 AM

@btmiller, the library file tat is not bein located is .so..can i use static flag while compiling??

thanks

jschiwal · 05-02-2012, 02:06 AM

You will need the static library, which is usually supplied in the -devel package version. Actually, the devel versions of dependencies is usually needed when compiling from source.any way. The static library versions have .a extensions.