Help With libjpeg

spinner

Apprentice

Posts: 10
Joined: 2006.10

Post: #1

Oct 4, 2006 — 04:02 PM

I need to use libjpeg for a project. I followed the install instructions I found online

Code:

tar zxvf jpegsrc.v6b.tar.gz

cd jpeg-6b

cp /usr/share/libtool/config.sub .

cp /usr/share/libtool/config.guess .

./configure --enable-shared --enable-static

make

sudo make install

sudo ranlib /usr/local/lib/libjpeg.a

And ended up with this...

Code:

zippy:/usr/local/lib luke$ ls

libjpeg.a       libjpeg.la

Now I need to link the files lib when I compile my project...

How do I do this?

I would have thought (the project is an opengl model viewer)

Code:

zippy:~/Desktop/project spinner$ g++ -o Viewer 3dsLoader.o ImageLoader.o Viewer.o -Wall -framework OpenGL -framework GLUT -L/usr/local/lib

but it doesn't work and I get

Code:

/usr/bin/ld: Undefined symbols:

jpeg_std_error(jpeg_error_mgr*)

jpeg_read_header(jpeg_decompress_struct*, int)

jpeg_read_scanlines(jpeg_decompress_struct*, unsigned char**, unsigned int)

jpeg_CreateDecompress(jpeg_decompress_struct*, int, unsigned long)

jpeg_start_decompress(jpeg_decompress_struct*)

jpeg_finish_decompress(jpeg_decompress_struct*)

jpeg_resync_to_restart(jpeg_decompress_struct*, int)

jpeg_destroy_decompress(jpeg_decompress_struct*)

collect2: ld returned 1 exit status

I have also tried

Code:

zippy:~/Desktop/project spinner$ g++ -o Viewer 3dsLoader.o ImageLoader.o Viewer.o -Wall -framework OpenGL -framework GLUT -ljpeg

/usr/bin/ld: Undefined symbols:

jpeg_std_error(jpeg_error_mgr*)

jpeg_read_header(jpeg_decompress_struct*, int)

jpeg_read_scanlines(jpeg_decompress_struct*, unsigned char**, unsigned int)

jpeg_CreateDecompress(jpeg_decompress_struct*, int, unsigned long)

jpeg_start_decompress(jpeg_decompress_struct*)

jpeg_finish_decompress(jpeg_decompress_struct*)

jpeg_resync_to_restart(jpeg_decompress_struct*, int)

jpeg_destroy_decompress(jpeg_decompress_struct*)

collect2: ld returned 1 exit status

Does this mean I haven't installed it correctly?

I actually had to create the /usr/local/lib directory, when I first tried to build the lib I got

Code:

/usr/bin/install -c libjpeg.la /usr/local/lib/libjpeg.la

install: /usr/local/lib/libjpeg.la: No such file or directory

make: *** [install-lib] Error 71

zippy:~/Desktop/jpeg/jpeg-6b spinner$ sudo mkdir /usr/local/lib

Sorry for the noob question.

Thanks

Spinner

spinner

Apprentice

Posts: 10
Joined: 2006.10

Post: #2

Oct 4, 2006 — 06:01 PM

Thanks to NCarter and ThemsAllTook on the iDG IRC channel, I now have an answer!

I thought I should post it incase anyone else has the same issue in the future.

My #include statement needed to specify it was a C lib, rather than C++

The correct way to do this is apparently

Code:

extern "C" {

#include <jpeglib.h>

}

Hope that helps someone.

Thanks to IRC channel for the prompt and friendly advice!

akb825

Moderator

Posts: 1,140
Joined: 2005.07

Post: #3

Oct 4, 2006 — 08:17 PM

You picked a good forum to ask this question: the MAF isn't exactly full of developers.

As I said there: most headers take into account C++ by having extern "C" between #ifdef __cplusplus ... #endif macros. Though you shouldn't have to worry about this very often with third party resources, it's a good thing to remember if you ever write anything in C which you then use in C++.

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