mirror of
https://github.com/Mercury-Language/mercury.git
synced 2025-12-13 12:53:53 +00:00
f1dbac2c98
Estimated hours taken: 1
README.Linux:
Use `ml --shared' rather than `ml --mercury-libs shared'
as the latter doesn't work.
Also don't talk worry about the difference between linking
just the Mercury libraries statically/shared -- assume
static or shared is an all-or-nothing concern (which it
probably is for most users).
44 lines
2.3 KiB
Plaintext
44 lines
2.3 KiB
Plaintext
This file documents just the Linux/x86 port.
|
|
For the Linux/PowerPC port, see README.Linux-PPC.
|
|
For the Linux/Alpha port, see README.Linux-Alpha.
|
|
(Ports to Linux on other architecures have not yet
|
|
been attempted, but should not be difficult.)
|
|
|
|
On Linux with a.out, shared libraries are not supported.
|
|
If you still have an old a.out system, the auto-configuration might
|
|
wrongly assume your Linux system uses ELF; if that happens, you will you
|
|
have to manually edit the EXT_FOR_SHARED_LIB variable in Mmake.common.
|
|
|
|
On Linux with ELF, shared libraries are supported. However, ELF shared
|
|
libraries require position-independent code, and (partly due to
|
|
limitations in our current compilation technology, but partly due to
|
|
limitations in the x86 architecture) this is quite costly for Mercury --
|
|
probably considerably more costly than it is for C.
|
|
|
|
Nevertheless, since shared libraries reduces disk usage, improve link
|
|
times, and allow run-time sharing of the Mercury libraries between
|
|
different applications, using them is a good idea.
|
|
|
|
Currently the default is that programs do *not* use the Mercury shared
|
|
libraries. (Probably it ought to be the other way around, but that
|
|
happened to be a little bit harder to implement. We may change this in
|
|
a future release.)
|
|
|
|
To use the shared libraries, you must compile your program with
|
|
`mmc --pic-reg' and link with `ml --shared' or add
|
|
`MGNUCFLAGS=--pic-reg' and `MLFLAGS=--shared' to your Mmake file.
|
|
|
|
Mercury code compiled with `--pic-reg' or with gcc's `-fpic' option has
|
|
what we shall call "PIC linkage", whereas Mercury code compiled without
|
|
these options has "non-PIC linkage". The static version of the Mercury
|
|
libraries has non-PIC linkage, while the shared version has PIC linkage.
|
|
Be careful that you do not try to link Mercury code with PIC linkage and
|
|
Mercury code with non-PIC linkage into the same executable, otherwise you
|
|
will probably get an obscure link error about `MR_grade_...' undefined
|
|
or `MR_runtime_grade' multiply defined.
|
|
(The reason for this is that standard non-PIC Mercury code uses the
|
|
`ebx' register in ways that are incompatible with its uses as the global
|
|
offset table pointer register in PIC code. If only the Intel
|
|
architecture wasn't so register-starved, we wouldn't need to use `ebx',
|
|
and then PIC and non-PIC code could be mixed without any problems.)
|