Re: GSoC Blog Post 0 - GCCprefab build system

[Wileam Yonatan Phan <wileamyp@outlook.com>]

Hi Jonathan,

Your build script is really impressive! I'm definitely not at that level yet
when it comes to Bash shell scripting. I'll start deciphering it and improve my
script accordingly.

By "relatively easy", I refer to the end-user of the script being able to
customize the build as s/he sees fit through the config file, and simply
running

$ ./build.sh config.cfg

substituting `config.cfg` with said build config file. So, one single line of
shell command instead of nine lines.

I also pepper my code with plenty of comments and strategically-placed
linebreaks for readability, which adds to the script length.

To be fair, most of the ~300 lines of the script belongs to the config file
interpreter function readcfg() because it uses if..elif..fi blocks instead of
case..esac blocks, and the bulk of the function is mostly for adding configure
flags, languages to compile, etc. (I plan to extend the script even further
once I start building GCC with GPU offloading support.)

Actually, the very first version of the script takes in a version string (like
your script) instead of a config file. You can access it here as a GitHub gist:
<
https://gist.github.com/wyphan/e2672336b80253a813abb795a5db567c/86eee347a8d26881a91356d9007790c5cff6654f
>
I later realized that relying on just the version string is insufficient for my
needs, specifically for adding configure flags like `--disable-bootstrap`,
which is hard-coded in that early version of the script.

Yes, you are correct that the script currently uses the tip of the
`releases/gcc-[version]` branches. Is that not the same as using the published
tarballs on the FTP server? I _do_ notice that these branches only get pushed
whenever a minor version or a patchlevel is released.

Thanks,
Wil

On Mon, 2022-06-13 at 16:26 +0100, Jonathan Wakely wrote:
> On Mon, 13 Jun 2022 at 14:34, Wileam Yonatan Phan wrote:
> > Hi Jonathan,
> > 
> > Thanks for the feedback. Regarding the linked page <
> > https://gcc.gnu.org/wiki/InstallingGCC
> > >
> > if you're referring to the part that tells you to use your distro's package
> > manager, yes that's indeed the simplest way to install GCC, but from pre-
> > built
> > binaries, not building directly from sources. But if you're referring to
> > the
> > example at the bottom of the page,
> 
> Yes, that's what I mean.
> 
> > this script does exactly that, but the build
> > process is automated based on the build configuration file.
> 
> Yes, it does that, but takes 400 lines of shell script to do so.
> 
> If you want "relatively easy ways to build GCC painlessly" then you
> can do it with nine lines of shell commands.
> 
> Or in about 80, for any non-prehistoric version, with no config file
> needed (just a single option to the script, the release number or
> snapshot name to build):
> https://gist.github.com/jwakely/95b3a790157f55d75e18f577e12b50d7#file-build_gcc_versions-sh
> 
> 
> My point is just that there are already easier ways to do it, not only
> by using spack or the OpenCoarrays build script.
> 
> N.B. your 
> https://github.com/wyphan/gccprefab/blob/main/gcc12.cfg
> 
> config file says "Latest GCC 12 Release" but actually builds from the
> tip of the branch, not a release.
>