help: gcc/ld doesn't see libraries consistently

[Daniel Barclay <dsb@smart.net>]

What might cause gcc not to be able to see some libraries that are 
in the same directories as other libraries it can see?


For example, these references work: 

	$ gcc test.c -lc
	$ gcc test.c -lcrypt 

but these do not:
	
	$ gcc test.c -lcfont
	/usr/bin/ld: cannot find -lcfont
	collect2: ld returned 1 exit status

	$ gcc test.c -lconsole
	/usr/bin/ld: cannot find -lconsole
	collect2: ld returned 1 exit status

	$ gcc test.c -lctutils
	/usr/bin/ld: cannot find -lctutils
	collect2: ld returned 1 exit status

	$ gcc test.c -lcom_err
	/usr/bin/ld: cannot find -lcom_err
	collect2: ld returned 1 exit status

(The test program is simply "main() {}".)


I can't figure out what the difference is.

ldconfig lists all those libraries:

	$ /sbin/ldconfig -p | grep "libc[^56]"
		libctutils.so.0 (libc6) => /lib/libctutils.so.0
		libcrypt.so.1 (libc6) => /lib/libcrypt.so.1
		libcrypt.so (libc6) => /usr/lib/libcrypt.so
		libconsole.so.0 (libc6) => /lib/libconsole.so.0
		libcom_err.so.2 (libc6) => /lib/libcom_err.so.2
		libcfont.so.0 (libc6) => /lib/libcfont.so.0
		libc.so.6 (libc6) => /lib/libc.so.6

Directory /lib also contains them all:

	bash-2.03$ ls -l /lib | grep "libc[^56]"
	-rwxr-xr-x    1 root     root       888596 Aug 14 18:11 libc-2.1.3.so
	lrwxrwxrwx    1 root     root           13 Aug 14 18:11 libc.so.6 -> libc-2.1.3.so
	lrwxrwxrwx    1 root     root           17 Aug 14 18:11 libcfont.so.0 -> libcfont.so.0.0.0
	-rw-r--r--    1 root     root        12332 Aug 14 18:11 libcfont.so.0.0.0
	lrwxrwxrwx    1 root     root           17 Aug 14 18:11 libcom_err.so.2 -> libcom_err.so.2.0
	-rw-r--r--    1 root     root         5244 Aug 14 18:11 libcom_err.so.2.0
	lrwxrwxrwx    1 root     root           19 Aug 14 18:11 libconsole.so.0 -> libconsole.so.0.0.0
	-rw-r--r--    1 root     root        61224 Aug 14 18:11 libconsole.so.0.0.0
	-rw-r--r--    1 root     root        20112 Aug 14 18:11 libcrypt-2.1.3.so
	lrwxrwxrwx    1 root     root           17 Aug 14 18:11 libcrypt.so.1 -> libcrypt-2.1.3.so
	lrwxrwxrwx    1 root     root           19 Aug 14 18:11 libctutils.so.0 -> libctutils.so.0.0.0
	-rw-r--r--    1 root     root        18252 Aug 14 18:11 libctutils.so.0.0.0



The file command shows seemingly normal results:

	bash-2.03$ file /lib/libc*
	/lib/libc-2.1.3.so:       ELF 32-bit LSB shared object, Intel 80386, version 1, stripped
	/lib/libc.so.6:           symbolic link to libc-2.1.3.so
	/lib/libcfont.so.0:       symbolic link to libcfont.so.0.0.0
	/lib/libcfont.so.0.0.0:   ELF 32-bit LSB shared object, Intel 80386, version 1, stripped
	/lib/libcom_err.so.2:     symbolic link to libcom_err.so.2.0
	/lib/libcom_err.so.2.0:   ELF 32-bit LSB shared object, Intel 80386, version 1, stripped
	/lib/libconsole.so.0:     symbolic link to libconsole.so.0.0.0
	/lib/libconsole.so.0.0.0: ELF 32-bit LSB shared object, Intel 80386, version 1, stripped
	/lib/libcrypt-2.1.3.so:   ELF 32-bit LSB shared object, Intel 80386, version 1, stripped
	/lib/libcrypt.so.1:       symbolic link to libcrypt-2.1.3.so
	/lib/libctutils.so.0:     symbolic link to libctutils.so.0.0.0
	/lib/libctutils.so.0.0.0: ELF 32-bit LSB shared object, Intel 80386, version 1, stripped


Any ideas?

The only thing I notice is that in the /lib directory listing,
the non-symbolic-link versions of libc and libcrypt have version 
numbers before the ".so" part:

	... libc-2.1.3.so
	... libc.so.6 -> libc-2.1.3.so
	... libcrypt-2.1.3.so
	... libcrypt.so.1 -> libcrypt-2.1.3.so


while for the other libraries the link name and the file name are
the same past the ".so" part:

	... libctutils.so.0 -> libctutils.so.0.0.0
	... libctutils.so.0.0.0
	...

Could that have any relationship to the problem?


Is there any documentation on exactly how gcc or ld finds libraries?
The manual pages mention a default search mechanism, but never say
exactly what that is or how it works (e.g., in relation to symbolic
links or multiple files with the same prefix).



Thanks,

Daniel
-- 
Daniel Barclay
dsb@smart.net
(Hmm.  A little worrisome:  http://www.junkbusters.com/cgi-bin/privacy
                            http://www.anonymizer.com/snoop.cgi )