* Linking to libraries in the ELF?
@ 2021-01-29 16:20 Maxime Devos
2021-03-09 21:04 ` Andy Wingo
0 siblings, 1 reply; 2+ messages in thread
From: Maxime Devos @ 2021-01-29 16:20 UTC (permalink / raw)
To: guile-devel
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Hi guilers,
I've got this crazy idea a few days ago, about the FFI interface.
When a program written in C is compiled with some shared libraries,
these libraries are referred to in special [insert ELF terminology
here] of the binary. I wonder if it would be reasonable and feasible
to do something similar for compiles guile modules?
C example:
$ readelf -d `which guile`
[-- Attachment #1.2: Type: text/plain, Size: 429 bytes --]
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libguile-3.0.so.1]
0x0000000000000001 (NEEDED) Shared library: [libgc.so.1]
0x0000000000000001 (NEEDED) Shared library: [libpthread.so.0]
0x0000000000000001 (NEEDED) Shared library: [libffi.so.7]
[snip]
0x000000000000001d (RUNPATH) Library runpath: [[snip]]
[snip]
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Hypothetical Scheme example:
$ readelf -d $HOME/.guix-profile/lib/guile/3.0/site-ccache/chickadee/audio/vorbis.go
[-- Attachment #1.4: Type: text/plain, Size: 539 bytes --]
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libvorbisfile.so.3]
0x000000000000001d (RUNPATH) Library runpath: [[snip]]
0x0000000037146003 (<unknown>: 37146003) 0x3000002
0x0000000037146002 (<unknown>: 37146002) 0xe8
0x0000000037146000 (<unknown>: 37146000) 0x20000
0x0000000037146001 (<unknown>: 37146001) 0xaaa0
0x000000000000000c (INIT) 0x6bd0
0x0000000037146004 (<unknown>: 37146004) 0x15530
0x0000000000000000 (NULL) 0x0
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This would require fleshing out some details though,
such as when to use RUNPATH and when not, cross-platform support,
where to find the libraries, some things I probably forgot.
WDYT?
Maxime
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Linking to libraries in the ELF?
2021-01-29 16:20 Linking to libraries in the ELF? Maxime Devos
@ 2021-03-09 21:04 ` Andy Wingo
0 siblings, 0 replies; 2+ messages in thread
From: Andy Wingo @ 2021-03-09 21:04 UTC (permalink / raw)
To: Maxime Devos; +Cc: guile-devel
On Fri 29 Jan 2021 17:20, Maxime Devos <maximedevos@telenet.be> writes:
> I've got this crazy idea a few days ago, about the FFI interface.
> When a program written in C is compiled with some shared libraries,
> these libraries are referred to in special [insert ELF terminology
> here] of the binary. I wonder if it would be reasonable and feasible
> to do something similar for compiles guile modules?
These sections of executables or shared libraries are actually
*interpreted* by the system dynamic library loader, ld.so. Guile has
its own loader, independent of ld.so, and so can implement this -- or do
more flexible things. In any case we probably shouldn't tie ourselves
to the particular implementation of a particular loader.
Of course, dynamic-link was... not a great interface. But with the
recent changes in git I think it can be fine (see "Foreign Libraries" in
the manual). For the FFI the bigger problem IMO is generating faster
foreign procedure bindings -- i.e. farther on the
compilation-vs-interpretation scale.
Cheers,
Andy
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