Directory structure of glibc and header files installed on Linux

Directory structure of glibc and header files installed on Linux

[Peng Yu]

Hi,

I'd like to know the complete list header files installed on Linux.

The directory structure is a little complicated. Could anybody help me
understand what they are? And what headers files are installed on
Linux?

Some files have the same name. What is their difference?

$ find -name stdlib.h
./include/stdlib.h
./include/bits/stdlib.h
./stdlib/stdlib.h
./stdlib/bits/stdlib.h

$ ls -gG --time-style=+""
total 12216
-rw-r--r--   1    18092  COPYING
-rw-r--r--   1    26530  COPYING.LIB
drwxr-xr-x  43     1376  ChangeLog.old
-rw-r--r--   1    33584  INSTALL
-rw-r--r--   1    18943  LICENSES
-rw-r--r--   1       50  MAINTAINERS
-rw-r--r--   1    49221  Makeconfig
-rw-r--r--   1    22147  Makefile
-rw-r--r--   1     1390  Makefile.help
-rw-r--r--   1      566  Makefile.in
-rw-r--r--   1    54260  Makerules
-rw-r--r--   1   301071  NEWS
-rw-r--r--   1     3151  README
-rw-r--r--   1    12888  Rules
-rw-r--r--   1     1230  abi-tags
-rw-r--r--   1     9813  aclocal.m4
drwxr-xr-x  23      736  argp
drwxr-xr-x  13      416  assert
drwxr-xr-x 135     4320  benchtests
drwxr-xr-x  84     2688  bits
drwxr-xr-x  18      576  catgets
-rw-r--r--   1     7850  config.h.in
-rw-r--r--   1     4053  config.make.in
-rwxr-xr-x   1   240311  configure
-rw-r--r--   1    56879  configure.ac
drwxr-xr-x   9      288  conform
drwxr-xr-x  35     1120  crypt
drwxr-xr-x  18      576  csu
drwxr-xr-x  13      416  ctype
drwxr-xr-x 120     3840  debug
drwxr-xr-x  38     1216  dirent
drwxr-xr-x  69     2208  dlfcn
drwxr-xr-x 628    20096  elf
-rw-r--r--   1     3937  extra-lib.mk
-rw-r--r--   1      940  gen-locales.mk
drwxr-xr-x  18      576  gmon
drwxr-xr-x   4      128  gnulib
drwxr-xr-x  27      864  grp
drwxr-xr-x  17      544  gshadow
drwxr-xr-x  10      320  hesiod
drwxr-xr-x  38     1216  htl
drwxr-xr-x  88     2816  hurd
drwxr-xr-x  46     1472  iconv
drwxr-xr-x 404    12928  iconvdata
drwxr-xr-x 157     5024  include
drwxr-xr-x 110     3520  inet
drwxr-xr-x  51     1632  intl
drwxr-xr-x 150     4800  io
-rw-r--r--   1     2025  libc-abis
drwxr-xr-x 224     7168  libio
-rw-r--r--   1      291  libof-iterator.mk
drwxr-xr-x  75     2400  locale
drwxr-xr-x 145     4640  localedata
drwxr-xr-x  51     1632  login
drwxr-xr-x  41     1312  mach
drwxr-xr-x  94     3008  malloc
drwxr-xr-x  70     2240  manual
drwxr-xr-x 507    16224  math
drwxr-xr-x   4      128  mathvec
drwxr-xr-x 182     5824  misc
drwxr-xr-x  49     1568  nis
drwxr-xr-x 362    11584  nptl
drwxr-xr-x  51     1632  nptl_db
drwxr-xr-x  48     1536  nscd
drwxr-xr-x  87     2784  nss
-rw-r--r--   1      358  o-iterator.mk
drwxr-xr-x  43     1376  po
drwxr-xr-x 307     9824  posix
drwxr-xr-x  17      544  pwd
drwxr-xr-x  98     3136  resolv
drwxr-xr-x  20      640  resource
drwxr-xr-x  72     2304  rt
drwxr-xr-x  55     1760  scripts
drwxr-xr-x  19      608  setjmp
drwxr-xr-x  17      544  shadow
-rw-r--r--   1     2409  shlib-versions
drwxr-xr-x  57     1824  signal
drwxr-xr-x  31      992  socket
drwxr-xr-x  92     2944  soft-fp
drwxr-xr-x 206     6592  stdio-common
drwxr-xr-x 245     7840  stdlib
drwxr-xr-x 159     5088  string
drwxr-xr-x  71     2272  sunrpc
drwxr-xr-x 214     6848  support
drwxr-xr-x  33     1056  sysdeps
drwxr-xr-x  22      704  sysvipc
drwxr-xr-x  18      576  termios
-rw-r--r--   1     3067  test-skeleton.c
drwxr-xr-x  80     2560  time
drwxr-xr-x  34     1088  timezone
-rw-r--r--   1      125  version.h
drwxr-xr-x 124     3968  wcsmbs
drwxr-xr-x  20      640  wctype

-- 
Regards,
Peng

Re: Directory structure of glibc and header files installed on Linux

[Florian Weimer]

* Peng Yu via Libc-help:

> I'd like to know the complete list header files installed on Linux.

The easiest way is to run build-many-glibcs.py and look at the install
trees.  The answer varies from architecture to architecture.

Thanks,
Florian

Re: Directory structure of glibc and header files installed on Linux

[Peng Yu]

I can see what files are in the ubuntu package libc6-dev. But that
does not help with where they come from and what the structure of the
glibc is. An explanation of the source tree would be helpful.

On 3/4/21, Florian Weimer <fweimer@redhat.com> wrote:
> * Peng Yu via Libc-help:
>
>> I'd like to know the complete list header files installed on Linux.
>
> The easiest way is to run build-many-glibcs.py and look at the install
> trees.  The answer varies from architecture to architecture.
>
> Thanks,
> Florian
>
>


-- 
Regards,
Peng

Re: Directory structure of glibc and header files installed on Linux

[Adhemerval Zanella]

On Thu, Mar 4, 2021 at 11:20 AM Peng Yu via Libc-help
<libc-help@sourceware.org> wrote:
>
> I can see what files are in the ubuntu package libc6-dev. But that
> does not help with where they come from and what the structure of the
> glibc is. An explanation of the source tree would be helpful.
>
> On 3/4/21, Florian Weimer <fweimer@redhat.com> wrote:
> > * Peng Yu via Libc-help:
> >
> >> I'd like to know the complete list header files installed on Linux.
> >
> > The easiest way is to run build-many-glibcs.py and look at the install
> > trees.  The answer varies from architecture to architecture.

The installed headers are defined by the rule 'headers' in the Makefile:

$ grep -w '\<headers\>.*:=' `find . -iname Makefile`
./dirent/Makefile:headers               := dirent.h bits/dirent.h
bits/dirent_ext.h
./pwd/Makefile:headers := pwd.h
./math/Makefile:headers         := math.h bits/mathcalls.h \
./resource/Makefile:headers       := sys/resource.h bits/resource.h
sys/vlimit.h        \
[...]

However each system can add extra installed headers with the
'sysdep_headers' rule:
 grep -w '\<sysdep_headers\>' `find . -iname Makefile`
./sysdeps/aarch64/Makefile:sysdep_headers += sys/ifunc.h
./sysdeps/x86/Makefile:sysdep_headers += sys/platform/x86.h
./sysdeps/powerpc/Makefile:sysdep_headers += sys/platform/ppc.h
./sysdeps/mach/hurd/Makefile:sysdep_headers += nfs/nfs.h
[...]

And each architecture can still override the header using the sysdeps folders.
For instance, the sysdeps/unix/sysv/linux/Makefile add the
bits/struct_stat.h, and
some architectures override it:

$ find . -iname struct_stat.h
./sysdeps/unix/sysv/linux/generic/bits/struct_stat.h
./sysdeps/unix/sysv/linux/sparc/bits/struct_stat.h
./sysdeps/unix/sysv/linux/alpha/bits/struct_stat.h
./sysdeps/unix/sysv/linux/s390/bits/struct_stat.h
./sysdeps/unix/sysv/linux/microblaze/bits/struct_stat.h
./sysdeps/unix/sysv/linux/x86/bits/struct_stat.h
./sysdeps/unix/sysv/linux/powerpc/bits/struct_stat.h
./sysdeps/unix/sysv/linux/ia64/bits/struct_stat.h
./sysdeps/unix/sysv/linux/m68k/bits/struct_stat.h
./sysdeps/unix/sysv/linux/bits/struct_stat.h
./sysdeps/unix/sysv/linux/mips/bits/struct_stat.h

That's why the simplest solution is as Florian has put it to build a
glibc to the target you want to
inspect and check the installed headers.

Re: Directory structure of glibc and header files installed on Linux

[Peng Yu]

Hi Adhemerval and Florian,

> That's why the simplest solution is as Florian has put it to build a
> glibc to the target you want to
> inspect and check the installed headers.

I don't understand this part. When it is installed, it does copies or
symlinks? If it is just copies, how to tell where they are originally
from? How to avoid the conflict between user installed libc vs the
system default installed libc (as. libc6-dev in debian lineage)?

Do you have to build glibc before running build-many-glibcs.py? How to
run build-many-glibcs.py? It seems that it have options. I am not sure
what options I should use. Could you show me the complete command?

Does macOS use glibc?

On macOS, I see this.

$ gcc -E -dD - <<< '#include <sys/socket.h>' |grep '^#define SOL_'
#define SOL_SOCKET 0xffff

On Linux, I see this. Is that macOS uses a completely different libc
library? Or glibc has a specific target for macOS?

$ gcc -E -dD - <<< '#include <sys/socket.h>' |grep '^#define SOL_'
#define SOL_RAW 255
#define SOL_DECNET 261
#define SOL_X25 262
#define SOL_PACKET 263
#define SOL_ATM 264
#define SOL_AAL 265
#define SOL_IRDA 266
#define SOL_NETBEUI 267
#define SOL_LLC 268
#define SOL_DCCP 269
#define SOL_NETLINK 270
#define SOL_TIPC 271
#define SOL_RXRPC 272
#define SOL_PPPOL2TP 273
#define SOL_BLUETOOTH 274
#define SOL_PNPIPE 275
#define SOL_RDS 276
#define SOL_IUCV 277
#define SOL_CAIF 278
#define SOL_ALG 279
#define SOL_NFC 280
#define SOL_KCM 281
#define SOL_TLS 282
#define SOL_XDP 283
#define SOL_SOCKET 1

-- 
Regards,
Peng

Re: Directory structure of glibc and header files installed on Linux

[Adhemerval Zanella]

On Thu, Mar 4, 2021 at 1:56 PM Peng Yu <pengyu.ut@gmail.com> wrote:
>
> Hi Adhemerval and Florian,
>
> > That's why the simplest solution is as Florian has put it to build a
> > glibc to the target you want to
> > inspect and check the installed headers.
>
> I don't understand this part. When it is installed, it does copies or
> symlinks? If it is just copies, how to tell where they are originally
> from? How to avoid the conflict between user installed libc vs the
> system default installed libc (as. libc6-dev in debian lineage)?

It always copy, there is no symlink involved in the installation. Also, there is
nothing preventing you to wreck your system by installing a glibc over the
system one (you should not do it unless you know *exactly* what you are
doing).

The usual process of installing the glibc is during either a work rebuild on a
sysroot (like Linux From Scratch does) or within a sysroot (like
build-many-glibcs.py
does).

>
> Do you have to build glibc before running build-many-glibcs.py? How to
> run build-many-glibcs.py? It seems that it have options. I am not sure
> what options I should use. Could you show me the complete command?

The build-many-glibcs.py requires some tools, like a working gcc, python3,
bison, and the other usual tools required to build gcc and glibc. The simplest
way to use is:

(1) glibc-git$ ./scripts/build-many-glibcs.py checkout
/path/to/place/source/and/binaries
(2) glibc-git$ ./scripts/build-many-glibcs.py host-libraries
(3) glibc-git$ ./scripts/build-many-glibcs.py compilers x86_64-linux-gnu
(4) glibc-git$ ./scripts/build-many-glibcs.py glibcs x86_64-linux-gnu

The (1) will download the required source (binutils, linux, gcc,
glibc, math libraries), (2) will
build the math libraries used in gcc built, (3) will build a bootstrap
compiler targetting
x86_64-linux-gnu, and finally (4) will build a glibc using the
bootstrap compiler built.

>
> Does macOS use glibc?

No, macOS uses its own libc implementation. And there is no glibc
support for macOS,
neither in plan.

>
> On macOS, I see this.
>
> $ gcc -E -dD - <<< '#include <sys/socket.h>' |grep '^#define SOL_'
> #define SOL_SOCKET 0xffff
>
> On Linux, I see this. Is that macOS uses a completely different libc
> library? Or glibc has a specific target for macOS?

Yes, macOS uses https://opensource.apple.com/source/Libc/

>
> $ gcc -E -dD - <<< '#include <sys/socket.h>' |grep '^#define SOL_'
> #define SOL_RAW 255
> #define SOL_DECNET 261
> #define SOL_X25 262
> #define SOL_PACKET 263
> #define SOL_ATM 264
> #define SOL_AAL 265
> #define SOL_IRDA 266
> #define SOL_NETBEUI 267
> #define SOL_LLC 268
> #define SOL_DCCP 269
> #define SOL_NETLINK 270
> #define SOL_TIPC 271
> #define SOL_RXRPC 272
> #define SOL_PPPOL2TP 273
> #define SOL_BLUETOOTH 274
> #define SOL_PNPIPE 275
> #define SOL_RDS 276
> #define SOL_IUCV 277
> #define SOL_CAIF 278
> #define SOL_ALG 279
> #define SOL_NFC 280
> #define SOL_KCM 281
> #define SOL_TLS 282
> #define SOL_XDP 283
> #define SOL_SOCKET 1
>
> --
> Regards,
> Peng

Re: Directory structure of glibc and header files installed on Linux

[Peng Yu]

Hi Adhemerval,

> The usual process of installing the glibc is during either a work rebuild on
> a
> sysroot (like Linux From Scratch does) or within a sysroot (like
> build-many-glibcs.py
> does).

These are too complicated at this moment. I do think that a verbal
explanation of the directory structure (target Linux as an example) is
more helpful.

>> Do you have to build glibc before running build-many-glibcs.py? How to
>> run build-many-glibcs.py? It seems that it have options. I am not sure
>> what options I should use. Could you show me the complete command?
>
> The build-many-glibcs.py requires some tools, like a working gcc, python3,
> bison, and the other usual tools required to build gcc and glibc. The
> simplest
> way to use is:

This also could be a problem due to the dependencies. Is there a
walkthrough with the exact set of commands based on a vanilla ubuntu
system?

For example, you mentioned sysroot. I am not familiar with it. An
exact sequence of commands should be helpful as the goal here is not
to learn sysroot.

> (1) glibc-git$ ./scripts/build-many-glibcs.py checkout
> /path/to/place/source/and/binaries
> (2) glibc-git$ ./scripts/build-many-glibcs.py host-libraries
> (3) glibc-git$ ./scripts/build-many-glibcs.py compilers x86_64-linux-gnu
> (4) glibc-git$ ./scripts/build-many-glibcs.py glibcs x86_64-linux-gnu
>
> The (1) will download the required source (binutils, linux, gcc,
> glibc, math libraries), (2) will
> build the math libraries used in gcc built, (3) will build a bootstrap
> compiler targetting
> x86_64-linux-gnu, and finally (4) will build a glibc using the
> bootstrap compiler built.


-- 
Regards,
Peng

Re: Directory structure of glibc and header files installed on Linux

[Konstantin Kharlamov]

On Thu, 2021-03-04 at 16:37 -0600, Peng Yu via Libc-help wrote:
> Hi Adhemerval,
> 
> > The usual process of installing the glibc is during either a work rebuild on
> > a
> > sysroot (like Linux From Scratch does) or within a sysroot (like
> > build-many-glibcs.py
> > does).
> 
> These are too complicated at this moment. I do think that a verbal
> explanation of the directory structure (target Linux as an example) is
> more helpful.
> 
> > > Do you have to build glibc before running build-many-glibcs.py? How to
> > > run build-many-glibcs.py? It seems that it have options. I am not sure
> > > what options I should use. Could you show me the complete command?
> > 
> > The build-many-glibcs.py requires some tools, like a working gcc, python3,
> > bison, and the other usual tools required to build gcc and glibc. The
> > simplest
> > way to use is:
> 
> This also could be a problem due to the dependencies. Is there a
> walkthrough with the exact set of commands based on a vanilla ubuntu
> system?
> 
> For example, you mentioned sysroot. I am not familiar with it. An
> exact sequence of commands should be helpful as the goal here is not
> to learn sysroot.
> 
> > (1) glibc-git$ ./scripts/build-many-glibcs.py checkout
> > /path/to/place/source/and/binaries
> > (2) glibc-git$ ./scripts/build-many-glibcs.py host-libraries
> > (3) glibc-git$ ./scripts/build-many-glibcs.py compilers x86_64-linux-gnu
> > (4) glibc-git$ ./scripts/build-many-glibcs.py glibcs x86_64-linux-gnu
> > 
> > The (1) will download the required source (binutils, linux, gcc,
> > glibc, math libraries), (2) will
> > build the math libraries used in gcc built, (3) will build a bootstrap
> > compiler targetting
> > x86_64-linux-gnu, and finally (4) will build a glibc using the
> > bootstrap compiler built.

FWIW, whenever I need to build a project I don't know how to build yet, I often look at how my distro does that. If it's something complicated (which seems to be the case with glibc), I use the configuration provided by my distro.

You said you're using Ubuntu. I found that Ubuntu provides a way to build a package from source by using `apt source …` and then `dpkg-buildpackage …`, see: https://askubuntu.com/a/246721/266507 (unless I misunderstand something, the `dpkg-buildpackage` will probably run a script that in turn runs `configure`, `make`, etc, and at the end would package a deb file).

Side note: apt will download sources for the version of glibc that is installed in your Ubuntu. Ubuntu is mostly known as a distro providing ancient software (except perhaps browsers), so the glibc you'll get will likely be very old. It may or may not be what you want.

However, even if it's not what you want, you could just replace the sources that apt downloaded for you with the actual latest version of glibc, and make it build them.

Re: Directory structure of glibc and header files installed on Linux

[Peng Yu]

> FWIW, whenever I need to build a project I don't know how to build yet, I
> often look at how my distro does that. If it's something complicated (which
> seems to be the case with glibc), I use the configuration provided by my
> distro.
>
> You said you're using Ubuntu. I found that Ubuntu provides a way to build a
> package from source by using `apt source …` and then `dpkg-buildpackage …`,
> see: https://askubuntu.com/a/246721/266507 (unless I misunderstand
> something, the `dpkg-buildpackage` will probably run a script that in turn
> runs `configure`, `make`, etc, and at the end would package a deb file).
>
> Side note: apt will download sources for the version of glibc that is
> installed in your Ubuntu. Ubuntu is mostly known as a distro providing
> ancient software (except perhaps browsers), so the glibc you'll get will
> likely be very old. It may or may not be what you want.

Debian packages are old. It just creates a .deb file. It introduces
another sets of tools which I don't know the details. If there are any
problems, I will not know how to fix along the way.

It is still too complicated. The original question is to understand
the directory structure. Then, the question became, compile glibc,
installing system from scratch ... I don't think approaches like this
makes sense. it makes a simple thing more complicated than necessary.

I think the main problem is that there is not a doc for the directory
structure of glibc. That should have been done.

-- 
Regards,
Peng

Re: Directory structure of glibc and header files installed on Linux

[Adhemerval Zanella]

> Il giorno 4 mar 2021, alle ore 23:38, Peng Yu <pengyu.ut@gmail.com> ha scritto:
> 
> 
>> 
>> FWIW, whenever I need to build a project I don't know how to build yet, I
>> often look at how my distro does that. If it's something complicated (which
>> seems to be the case with glibc), I use the configuration provided by my
>> distro.
>> 
>> You said you're using Ubuntu. I found that Ubuntu provides a way to build a
>> package from source by using `apt source …` and then `dpkg-buildpackage …`,
>> see: https://askubuntu.com/a/246721/266507 (unless I misunderstand
>> something, the `dpkg-buildpackage` will probably run a script that in turn
>> runs `configure`, `make`, etc, and at the end would package a deb file).
>> 
>> Side note: apt will download sources for the version of glibc that is
>> installed in your Ubuntu. Ubuntu is mostly known as a distro providing
>> ancient software (except perhaps browsers), so the glibc you'll get will
>> likely be very old. It may or may not be what you want.
> 
> Debian packages are old. It just creates a .deb file. It introduces
> another sets of tools which I don't know the details. If there are any
> problems, I will not know how to fix along the way.
> 
> It is still too complicated. The original question is to understand
> the directory structure. Then, the question became, compile glibc,
> installing system from scratch ... I don't think approaches like this
> makes sense. it makes a simple thing more complicated than necessary.
> 

The problem here is we giving you the readily available information and steps on how you can proceed and obtain what you initially want, but you instead want *us* to spend time compiling and summarizes games instead of do yourself the research.

> I think the main problem is that there is not a doc for the directory
> structure of glibc. That should have been done.

I do not disagree, if you want to contribute I can give you access to glibc wiki and help you document this properly.

Re: Directory structure of glibc and header files installed on Linux

[Adhemerval Zanella]

On 04/03/2021 19:37, Peng Yu wrote:
> Hi Adhemerval,
> 
>> The usual process of installing the glibc is during either a work rebuild on
>> a
>> sysroot (like Linux From Scratch does) or within a sysroot (like
>> build-many-glibcs.py
>> does).
> 
> These are too complicated at this moment. I do think that a verbal
> explanation of the directory structure (target Linux as an example) is
> more helpful.

Sorry, but you will need to get used to some terminology and how toolchain
work.  You can either read the build-many-glibcs.py script and see how
it accomplish the bootstrap you check with multiple online resources on
how this is done (for instance on how crosstool-ng does it [1] or how Linux
from Scratch work [2]).

> 
>>> Do you have to build glibc before running build-many-glibcs.py? How to
>>> run build-many-glibcs.py? It seems that it have options. I am not sure
>>> what options I should use. Could you show me the complete command?
>>
>> The build-many-glibcs.py requires some tools, like a working gcc, python3,
>> bison, and the other usual tools required to build gcc and glibc. The
>> simplest
>> way to use is:
> 
> This also could be a problem due to the dependencies. Is there a
> walkthrough with the exact set of commands based on a vanilla ubuntu
> system?

I just gave you the simplest way on how to create a bootstrap compiler,
did at least try and checked the results?

> 
> For example, you mentioned sysroot. I am not familiar with it. An
> exact sequence of commands should be helpful as the goal here is not
> to learn sysroot.

A sysroot is a folder which contains a minimal filesystem (especially 
libraries, the C library and header files). I just paste the *exactly*
sequence of command using build-many-glibcs.py to create one using
gcc targeting glibc. You will need to read build-many-glibcs.py [3]
to check exactly on how it accomplish it,

> 
>> (1) glibc-git$ ./scripts/build-many-glibcs.py checkout
>> /path/to/place/source/and/binaries
>> (2) glibc-git$ ./scripts/build-many-glibcs.py host-libraries
>> (3) glibc-git$ ./scripts/build-many-glibcs.py compilers x86_64-linux-gnu
>> (4) glibc-git$ ./scripts/build-many-glibcs.py glibcs x86_64-linux-gnu
>>
>> The (1) will download the required source (binutils, linux, gcc,
>> glibc, math libraries), (2) will
>> build the math libraries used in gcc built, (3) will build a bootstrap
>> compiler targetting
>> x86_64-linux-gnu, and finally (4) will build a glibc using the
>> bootstrap compiler built.
> 
> 

[1] https://crosstool-ng.github.io/docs/toolchain-construction/
[2] http://www.linuxfromscratch.org/
[3] https://sourceware.org/git/?p=glibc.git;a=blob;f=scripts/build-many-glibcs.py;h=580d25e8ee4b3ff5f99fb957e6e533035bcc4ebc;hb=HEAD

Re: Directory structure of glibc and header files installed on Linux

[Peng Yu]

> A sysroot is a folder which contains a minimal filesystem (especially
> libraries, the C library and header files). I just paste the *exactly*
> sequence of command using build-many-glibcs.py to create one using
> gcc targeting glibc. You will need to read build-many-glibcs.py [3]
> to check exactly on how it accomplish it,

I am referring to the exact sequence of commands to make sysroot.
Basically, all commands need for vanilla ubuntu are needed (only
sysroot is need before running build-many-glibcs.py ?). Google search
of sysroot is not very helpful on how to use it.

https://stackoverflow.com/questions/39920712/what-is-a-sysroot-exactly-and-how-do-i-create-one

So once sysroot is create, then the following commands can be used?
All the original glibc installed in the system will not be affected?

>>> (1) glibc-git$ ./scripts/build-many-glibcs.py checkout
>>> /path/to/place/source/and/binaries
>>> (2) glibc-git$ ./scripts/build-many-glibcs.py host-libraries
>>> (3) glibc-git$ ./scripts/build-many-glibcs.py compilers x86_64-linux-gnu
>>> (4) glibc-git$ ./scripts/build-many-glibcs.py glibcs x86_64-linux-gnu
>>>
>>> The (1) will download the required source (binutils, linux, gcc,
>>> glibc, math libraries), (2) will
>>> build the math libraries used in gcc built, (3) will build a bootstrap
>>> compiler targetting
>>> x86_64-linux-gnu, and finally (4) will build a glibc using the
>>> bootstrap compiler built.
>>
>>
>
> [1] https://crosstool-ng.github.io/docs/toolchain-construction/

I don't need cross compilation. Why is this relevant?

> [2] http://www.linuxfromscratch.org/

What is the relation of the above instruction to arch linux?

> [3]
> https://sourceware.org/git/?p=glibc.git;a=blob;f=scripts/build-many-glibcs.py;h=580d25e8ee4b3ff5f99fb957e6e533035bcc4ebc;hb=HEAD

There are almost two thousand lines of code with too much code about
dealing with command-line options. It is definitely not minimal for
learning purposes. Does it really take so many lines of code. If the
target is just for intel architecture, It sounds like a bash script
with barely minimal code should be much shorter.

-- 
Regards,
Peng