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

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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