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libv4l-0.1 compiule problem

Hi. I grabbed the latest source, compiled it for 64 bit, made clean and then wanted a 32 bit version. The site
http://hansdegoede.livejournal.com/7622.html gives this line

make PREFIX=/usr CFLAGS=-m32 LDFLAGS=-m32

That failed for the lack of libv4lconvert.h (in ../include). A symlink fixed that. Now I get this

Code:

gcc -fpic -m32 -o libv4lconvert/spca501.o -c libv4lconvert/spca501.c

gcc -fpic -m32 -o libv4lconvert/bayer.o -c libv4lconvert/bayer.c

gcc -m32 -Wl,-soname,libv4lconvert.so.0 -o lib/libv4lconvert.so.0 libv4lconvert/libv4lconvert.o libv4lconvert/tinyjpeg.o libv4lconvert/jidctflt.o libv4lconvert/spca561-decompress.o libv4lconvert/rgbyuv.o libv4lconvert/spca501.o libv4lconvert/bayer.o

/usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../lib/crt1.o: In function `_start':

(.text+0x18): undefined reference to `main'

collect2: ld returned 1 exit status

make: *** [lib/libv4lconvert.so.0] Error 1

which, at a guess, is glibc related My installed glibc stuff is

Code:

 bash-3.1$ ls /var/log/packages/glibc*

/var/log/packages/glibc-2.7-x86_64_slamd64-9              /var/log/packages/glibc-solibs-2.7-x86_64_slamd64-9

/var/log/packages/glibc-i18n-2.7-noarch_slamd64-9    /var/log/packages/glibc-zoneinfo-2.7-noarch_slamd64-9

/var/log/packages/glibc-profile-2.7-x86_64_slamd64-9  /var/log/packages/glibc32-2.7-x86_64_slamd64-9

Any ideas please? I do seem to have a 32bit compat library there.

Edit: /usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../lib/crt1.o actually exists, is 32 bit and has a function called 'main' according to readelf :-o.

Quote:

Originally Posted by business_kid (Post 3796568)

Code:

gcc -fpic -m32 -o libv4lconvert/spca501.o -c libv4lconvert/spca501.c

gcc -fpic -m32 -o libv4lconvert/bayer.o -c libv4lconvert/bayer.c

gcc -m32 -Wl,-soname,libv4lconvert.so.0 -o lib/libv4lconvert.so.0 libv4lconvert/libv4lconvert.o libv4lconvert/tinyjpeg.o libv4lconvert/jidctflt.o libv4lconvert/spca561-decompress.o libv4lconvert/rgbyuv.o libv4lconvert/spca501.o libv4lconvert/bayer.o

/usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../lib/crt1.o: In function `_start':

(.text+0x18): undefined reference to `main'

collect2: ld returned 1 exit status

make: *** [lib/libv4lconvert.so.0] Error 1

Edit: /usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../lib/crt1.o actually exists, is 32 bit and has a function called 'main' according to readelf :-o.

First, if crt1.o really does have a *defined* symbol called 'main' then something is very, very wrong! If you look closely you should see that it uses a symbol called main - readelf will give you a list of symbols the object file uses as well as ones it defines.

Second, your problem is that the -shared flag isn't specified in the gcc command to create the .so library.

Thanks for the reply John. Adding the shared flag to CFLAGS and LDFLAGS allowed it to compile. Thank heavens for search options in a man page!

Just FYI Here's what ctrl.o shows from readelf

Code:

There are no program headers in this file.



Relocation section '.rel.text' at offset 0x49c contains 4 entries:

 Offset    Info    Type            Sym.Value  Sym. Name

0000000c  00000a01 R_386_32          00000000  __libc_csu_fini

00000011  00000c01 R_386_32          00000000  __libc_csu_init

00000018  00000d01 R_386_32          00000000  main

0000001d  00001002 R_386_PC32        00000000  __libc_start_main

Ah - don't know what option you're passing to readelf, but if you use --symbols you'll get output like:

Code:

Symbol table '.symtab' contains 25 entries:

  Num:    Value  Size Type    Bind  Vis      Ndx Name

...

    20: 00000000    0 NOTYPE  GLOBAL DEFAULT  UND main

Which shows the symbol main to be UND (undefined). A simpler program with simpler output is nm if you just want to look at which symbols there are:

Code:

$ nm /usr/lib/crt1.o

00000000 R _IO_stdin_used

00000000 D __data_start

        U __libc_csu_fini

        U __libc_csu_init

        U __libc_start_main

00000000 R _fp_hw

00000000 T _start

00000000 W data_start

        U main

Where 'U' means undefined - you can also just pass it --defined to look at what that .o/.a/.so file defines.

Thx. I passed readelf the '-a'. I'm not a programmer, but an LFS builder, so one gets fairly competent at failed compiles without fully knowing what is going on.