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docs: update the section about the wrapper

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The wrapper is no longer needed when building
non-shared companion libraries. Document that.
This commit is contained in:
Yann E. MORIN" 2010-04-28 22:24:01 +02:00
parent 572a4e4bd7
commit 52304e2e56
1 changed files with 20 additions and 8 deletions
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docs/overview.txt
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@ -447,22 +447,31 @@ Tools wrapper |
--------------+
Starting with gcc-4.3 come two new dependencies: GMP and MPFR. With gcc-4.4,
come three new ones: GMP, PPL and CLooG/ppl. These are libraries that enable
advanced features to gcc. Additionally, some of the libraries can be used by
binutils and gdb. Unfortunately, not all systems on which crosstool-NG runs
have all of those libraries. And for those that do, the versions of those
libraries may be older than the version required by gcc.
come three new ones: PPL, CLooG/ppl and MPC. With gcc-4.5 again comes a new
dependency on libelf. These are libraries that enable advanced features to
gcc. Additionally, some of those libraries can be used by binutils and gdb.
Unfortunately, not all systems on which crosstool-NG runs have all of those
libraries. And for those that do, the versions of those libraries may be
older than the version required by gcc (and binutils and gdb). To date,
Debian stable (aka Lenny) is lagging behind on some, and is missing the
others.
This is why crosstool-NG builds its own set of libraries as part of the
toolchain.
The libraries are built as shared libraries, because building them as static
libraries has some short-comings. This poses no problem at build time, as
The companion libraries can be built either as static libraries, or as shared
libraries. The default is to build static libraries, and is the safe way.
If you decide to use static companion libraries, then you can stop reading
this section.
But if you prefer to have shared libraries, then read on...
Building shared companion libraries poses no problem at build time, as
crosstool-NG correctly points gcc (and binutils and gdb) to the correct
place where our own version of the libraries are installed. But it poses
a problem when gcc et al. are run: the place where the libraries are is most
probably not known to the host dynamic linker. Still worse, if the host system
has its own versions, then ld.so would load the wrong library!
has its own versions, then ld.so would load the wrong libraries!
So we have to force the dynamic linker to load the correct version. We do this
by using the LD_LIBRARY_PATH variable, that informs the dynamic linker where
@ -489,6 +498,9 @@ So, the default wrapper installed with your toolchain is the shell script.
If you know that your system is missing a shell, then you shall use the C
wrapper (and report back whether it works, or does not work, for you).
A final word on the subject: do not build shared libraries. Build them
static, and you'll be safe.
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