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From: antispam@fricas.org (Waldek Hebisch)
Newsgroups: comp.lang.c
Subject: Re: else ladders practice
Date: Sun, 24 Nov 2024 22:21:59 -0000 (UTC)
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Bart <bc@freeuk.com> wrote:
> On 24/11/2024 20:01, Keith Thompson wrote:
>> Bart <bc@freeuk.com> writes:
>> [...]
>>> Most of a gcc installation is hundreds of header and archive (.a)
>>> files for various libraries. There might be 32-bit and 64-bit
>>> versions. I understand that. But it also makes it hard to isolate the
>>> core compiler.
>> [...]
>> 
>> That doesn't agree with my observations.
>> 
>> Of course most of the headers and libraries are not part of gcc itself.
>> As usual, you refer to the entire implementation as "gcc".
>> 
>> I've built gcc 14.2.0 and glibc 2.40 from source on Ubuntu 22.04.5,
>> installing each into a new directory.
>> 
>> The gcc installation is about 5.6 GB, reduced to about 1.9 GB if I strip
>> the executables.
> 
> That's even huger than mine! So, that are those 3.7GB full of? What does 
> the 1.9GB of executables do?

The 3.7GB is debug info which Keith removed.  gcc is now written in
C++ and when you compile with debug info on about 90% of executable
is debug info.

>> Of course there are other libraries that can be used with gcc, and they
>> could take a lot of space -- but they're not part of gcc.
> 
> So, what /is/ gcc? What's the minimum installation that can compile 
> hello.c to hello.s for example?
> 
> I've done that experiment on my TDM version, and the answer appears to 
> be about 40MB in this directory structure:
> 
>  Directory of c:\tdm\bin
> 24/07/2024  10:21         1,926,670 gcc.exe
> 24/07/2024  10:21         2,279,503 libisl-23.dll
> 24/07/2024  10:22           164,512 libmpc-3.dll
> 24/07/2024  10:22           702,852 libmpfr-6.dll
> 
>  Directory of c:\tdm\libexec\gcc\x86_64-w64-mingw32\14.1.0
> 24/07/2024  10:24        34,224,654 cc1.exe

That is reasonably good apporximation to the compiler proper.
More preciesly, to compile you need 'cc1.exe' and libraries
it uses.  On Linux I get:
ldd /sklad0/p0/kompi/gcc_pp/usr_14.2.0/libexec/gcc/x86_64-pc-linux-gnu/14.2.0/cc1
	linux-vdso.so.1 (0x00007ffc8a8f2000)
	libmpc.so.3 => /lib/x86_64-linux-gnu/libmpc.so.3 (0x00007fa55e071000)
	libmpfr.so.6 => /lib/x86_64-linux-gnu/libmpfr.so.6 (0x00007fa55dfb7000)
	libgmp.so.10 => /lib/x86_64-linux-gnu/libgmp.so.10 (0x00007fa55df36000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fa55de57000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fa55dc76000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fa55e0a9000)

This is list of libraries needed by 'cc1'.  /lib64/ld-linux-x86-64.so.2,
libc.so.6 and libm.so.6 are system libraries needed by almost all
things.  linux-vdso.so.1 is virtual thing, IIUC there is nothing
corresponding on the disc.

>  Directory of c:\tdm\x86_64-w64-mingw32\include
> 17/01/2021  17:33               368 stddef.h
> 27/03/2021  20:07             2,924 stdio.h
> 
>                7 File(s)     39,301,483 bytes
> 
> Here I cheated a little and used the minimum std headers from my 
> compiler, otherwise I could have spent an hour chasing down dozens of 
> obscure nested headers that gcc's stdio.h likes to make use of.

Yes, beside compiler propor you also need headers used by the C
file.

> Is /this/ gcc then? Will you agree that it is by no means clear what 
> 'gcc' includes, or what to call the part of a gcc installed bundle that 
> is not technically gcc?
> 
> A more useful installation would of course need more standard headers, 
> an assembler, linker, and whatever .a files are needed to provide the 
> standard library.

Debian splits gcc into several package.  One of them is 'cpp-12'
and this one gives you 'cc1' (that is compiler proper).  There
is 'gcc-12' which actually mainly provides extra features like
lto (link time optimization), sanitizers.  It also provides
things like 'collect2' (wrapper around linker to have extra
features) and 'x86_64-linux-gnu-gcc-ar-12' (I do not know why
this is needed).  'gcc-12' pulls several dependencies:

cpp-12, gcc-12-base, libcc1-0, binutils, libgcc-12-dev,
libc6, libgcc-s1, libgmp10, libisl23, libmpc3, libmpfr6,
libstdc++6, libzstd1, zlib1g

binutils gives you assembler and linker, libgcc-s1 is shared
support library (needed to run dynamically linked programs),
libgcc-12-dev contains startup files (needed to link any program)
and bunch of libraries and headers supporting extra features,
libgmp10, libmpc3, libmpfr6 (and of course libc6) are needed
to run compiler.  I am not sure about libisl23, libstdc++6,
libzstd1, zlib1g.

To get standard header files you need to install 'libc6-dev'.

> With clang, it is easier: apparently everything needed to do the above, 
> other than header files, is contained with a 120MB executable clang.exe.

Probably you means things needed to run the compiler.  clang compiled
executable need libraries too, on Debian this is shared with gcc.

-- 
                              Waldek Hebisch