6.9. Glibc-2.5

The Glibc package contains the main C library. This library provides the basic routines for allocating memory, searching directories, opening and closing files, reading and writing files, string handling, pattern matching, arithmetic, and so on.

Approximate build time: 19.5 SBU testsuite included
Required disk space: 556 MB testsuite included

6.9.1. Installation of Glibc

[Note]

Note

Some packages outside of LFS suggest installing GNU libiconv in order to translate data from one encoding to another. The project's home page (http://www.gnu.org/software/libiconv/) says “This library provides an iconv() implementation, for use on systems which don't have one, or whose implementation cannot convert from/to Unicode.” Glibc provides an iconv() implementation and can convert from/to Unicode, therefore libiconv is not required on an LFS system.

The Glibc build system is self-contained and will install perfectly, even though the compiler specs file and linker are still pointing at /tools. The specs and linker cannot be adjusted before the Glibc install because the Glibc autoconf tests would give false results and defeat the goal of achieving a clean build.

The glibc-libidn tarball adds support for internationalized domain names (IDN) to Glibc. Many programs that support IDN require the full libidn library, not this add-on (see http://www.linuxfromscratch.org/blfs/view/svn/general/libidn.html). Unpack the tarball from within the Glibc source directory:

tar -xvf ../glibc-libidn-2.5.tar.bz2
mv glibc-libidn-2.5 libidn

In the vi_VN.TCVN locale, bash enters an infinite loop at startup. It is unknown whether this is a bash bug or a Glibc problem. Disable installation of this locale in order to avoid the problem:

sed -i '/vi_VN.TCVN/d' localedata/SUPPORTED

When running make install, a script called test-installation.pl performs a small sanity test on our newly installed Glibc. However, because our toolchain still points to the /tools directory, the sanity test would be carried out against the wrong Glibc. We can force the script to check the Glibc we have just installed with the following:

sed -i \
's|libs -o|libs -L/usr/lib -Wl,-dynamic-linker=/lib/ld-linux.so.2 -o|' \
        scripts/test-installation.pl

The Glibc documentation recommends building Glibc outside of the source directory in a dedicated build directory:

mkdir -v ../glibc-build
cd ../glibc-build

Prepare Glibc for compilation:

../glibc-2.5/configure --prefix=/usr \
    --disable-profile --enable-add-ons \
    --enable-kernel=2.6.0 --libexecdir=/usr/lib/glibc

The meaning of the new configure options:

--libexecdir=/usr/lib/glibc

This changes the location of the pt_chown program from its default of /usr/libexec to /usr/lib/glibc.

Compile the package:

make
[Important]

Important

In this section, the test suite for Glibc is considered critical. Do not skip it under any circumstance.

Test the results:

make -k check 2>&1 | tee glibc-check-log
grep Error glibc-check-log

You will probably see an expected (ignored) failure in the posix/annexc test. In addition the Glibc test suite is somewhat dependent on the host system. This is a list of the most common issues:

  • The nptl/tst-clock2 and tst-attr3 tests sometimes fail. The reason is not completely understood, but indications are that a heavy system load can trigger these failures.

  • The math tests sometimes fail when running on systems where the CPU is not a relatively new genuine Intel or authentic AMD processor.

  • If you have mounted the LFS partition with the noatime option, the atime test will fail. As mentioned in Section 2.4, “Mounting the New Partition”, do not use the noatime option while building LFS.

  • When running on older and slower hardware or on systems under load, some tests can fail because of test timeouts being exceeded.

Though it is a harmless message, the install stage of Glibc will complain about the absence of /etc/ld.so.conf. Prevent this warning with:

touch /etc/ld.so.conf

Install the package:

make install

The locales that can make the system respond in a different language were not installed by the above command. None of the locales are required, but if some of them are missing, testsuites of the future packages would skip important testcases.

Individual locales can be installed using the localedef program. E.g., the first localedef command below combines the /usr/share/i18n/locales/de_DE charset-independent locale definition with the /usr/share/i18n/charmaps/ISO-8859-1.gz charmap definition and appends the result to the /usr/lib/locale/locale-archive file. The following instructions will install the minimum set of locales necessary for the optimal coverage of tests:

mkdir -pv /usr/lib/locale
localedef -i de_DE -f ISO-8859-1 de_DE
localedef -i de_DE@euro -f ISO-8859-15 de_DE@euro
localedef -i en_HK -f ISO-8859-1 en_HK
localedef -i en_PH -f ISO-8859-1 en_PH
localedef -i en_US -f ISO-8859-1 en_US
localedef -i en_US -f UTF-8 en_US.UTF-8
localedef -i es_MX -f ISO-8859-1 es_MX
localedef -i fa_IR -f UTF-8 fa_IR
localedef -i fr_FR -f ISO-8859-1 fr_FR
localedef -i fr_FR@euro -f ISO-8859-15 fr_FR@euro
localedef -i fr_FR -f UTF-8 fr_FR.UTF-8
localedef -i it_IT -f ISO-8859-1 it_IT
localedef -i ja_JP -f EUC-JP ja_JP

In addition, install the locale for your own country, language and character set.

Alternatively, install all locales listed in the glibc-2.5/localedata/SUPPORTED file (it includes every locale listed above and many more) at once with the following time-consuming command:

make localedata/install-locales

Then use the localedef command to create and install locales not listed in the glibc-2.5/localedata/SUPPORTED file in the unlikely case if you need them.

6.9.2. Configuring Glibc

The /etc/nsswitch.conf file needs to be created because, although Glibc provides defaults when this file is missing or corrupt, the Glibc defaults do not work well in a networked environment. The time zone also needs to be configured.

Create a new file /etc/nsswitch.conf by running the following:

cat > /etc/nsswitch.conf << "EOF"
# Begin /etc/nsswitch.conf

passwd: files
group: files
shadow: files

hosts: files dns
networks: files

protocols: files
services: files
ethers: files
rpc: files

# End /etc/nsswitch.conf
EOF

One way to determine the local time zone, run the following script:

tzselect

After answering a few questions about the location, the script will output the name of the time zone (e.g., America/Edmonton). There are also some other possible timezones listed in /usr/share/zoneinfo such as Canada/Eastern or EST5EDT that are not identified by the script but can be used.

Then create the /etc/localtime file by running:

cp -v --remove-destination /usr/share/zoneinfo/<xxx> \
    /etc/localtime

Replace <xxx> with the name of the time zone selected (e.g., Canada/Eastern).

The meaning of the cp option:

--remove-destination

This is needed to force removal of the already existing symbolic link. The reason for copying the file instead of using a symlink is to cover the situation where /usr is on a separate partition. This could be important when booted into single user mode.

6.9.3. Configuring the Dynamic Loader

By default, the dynamic loader (/lib/ld-linux.so.2) searches through /lib and /usr/lib for dynamic libraries that are needed by programs as they are run. However, if there are libraries in directories other than /lib and /usr/lib, these need to be added to the /etc/ld.so.conf file in order for the dynamic loader to find them. Two directories that are commonly known to contain additional libraries are /usr/local/lib and /opt/lib, so add those directories to the dynamic loader's search path.

Create a new file /etc/ld.so.conf by running the following:

cat > /etc/ld.so.conf << "EOF"
# Begin /etc/ld.so.conf

/usr/local/lib
/opt/lib

# End /etc/ld.so.conf
EOF

6.9.4. Contents of Glibc

Installed programs: catchsegv, gencat, getconf, getent, iconv, iconvconfig, ldconfig, ldd, lddlibc4, locale, localedef, mtrace, nscd, pcprofiledump, pt_chown, rpcgen, rpcinfo, sln, sprof, tzselect, xtrace, zdump, and zic
Installed libraries: ld.so, libBrokenLocale.{a,so}, libSegFault.so, libanl.{a,so}, libbsd-compat.a, libc.{a,so}, libcidn.so, libcrypt.{a,so}, libdl.{a,so}, libg.a, libieee.a, libm.{a,so}, libmcheck.a, libmemusage.so, libnsl.a, libnss_compat.so, libnss_dns.so, libnss_files.so, libnss_hesiod.so, libnss_nis.so, libnss_nisplus.so, libpcprofile.so, libpthread.{a,so}, libresolv.{a,so}, librpcsvc.a, librt.{a,so}, libthread_db.so, and libutil.{a,so}

Short Descriptions

catchsegv

Can be used to create a stack trace when a program terminates with a segmentation fault

gencat

Generates message catalogues

getconf

Displays the system configuration values for file system specific variables

getent

Gets entries from an administrative database

iconv

Performs character set conversion

iconvconfig

Creates fastloading iconv module configuration files

ldconfig

Configures the dynamic linker runtime bindings

ldd

Reports which shared libraries are required by each given program or shared library

lddlibc4

Assists ldd with object files

locale

Prints various information about the current locale

localedef

Compiles locale specifications

mtrace

Reads and interprets a memory trace file and displays a summary in human-readable format

nscd

A daemon that provides a cache for the most common name service requests

pcprofiledump

Dumps information generated by PC profiling

pt_chown

A helper program for grantpt to set the owner, group and access permissions of a slave pseudo terminal

rpcgen

Generates C code to implement the Remote Procecure Call (RPC) protocol

rpcinfo

Makes an RPC call to an RPC server

sln

A statically linked ln program

sprof

Reads and displays shared object profiling data

tzselect

Asks the user about the location of the system and reports the corresponding time zone description

xtrace

Traces the execution of a program by printing the currently executed function

zdump

The time zone dumper

zic

The time zone compiler

ld.so

The helper program for shared library executables

libBrokenLocale

Used internally by Glibc as a gross hack to get broken programs (e.g., some Motif applications) running. See comments in glibc-2.5/locale/broken_cur_max.c for more information

libSegFault

The segmentation fault signal handler, used by catchsegv

libanl

An asynchronous name lookup library

libbsd-compat

Provides the portability needed in order to run certain Berkey Software Distribution (BSD) programs under Linux

libc

The main C library

libcidn

Used internally by Glibc for handling internationalized domain names in the getaddrinfo() function

libcrypt

The cryptography library

libdl

The dynamic linking interface library

libg

Dummy library containing no functions. Previously was a runtime library for g++

libieee

Linking in this module forces error handling rules for math functions as defined by the Institute of Electrical and Electronic Engineers (IEEE). The default is POSIX.1 error handling

libm

The mathematical library

libmcheck

Turns on memory allocation checking when linked to

libmemusage

Used by memusage to help collect information about the memory usage of a program

libnsl

The network services library

libnss

The Name Service Switch libraries, containing functions for resolving host names, user names, group names, aliases, services, protocols, etc.

libpcprofile

Contains profiling functions used to track the amount of CPU time spent in specific source code lines

libpthread

The POSIX threads library

libresolv

Contains functions for creating, sending, and interpreting packets to the Internet domain name servers

librpcsvc

Contains functions providing miscellaneous RPC services

librt

Contains functions providing most of the interfaces specified by the POSIX.1b Realtime Extension

libthread_db

Contains functions useful for building debuggers for multi-threaded programs

libutil

Contains code for “standard” functions used in many different Unix utilities