Le 07/03/2013 19:51, Matt Burgess a écrit :
> On Thu, 2013-03-07 at 14:57 +0100, Pierre Labastie wrote:
>
>> Please add --with-sysroot to the configure switches in binutils-pass2.
>> It is harmless (just adds a feature to ld), and corrects that bug.
> I think you meant --with-build-sysroot, right? The configure help
> output for that says
>
> --with-build-sysroot=SYSROOT
> use sysroot as the system root during the build
>
> So, I assume just '--with-build-sysroot' is enough, i.e. setting it to a
> null value? I still don't understand what that flag does and why/how it
> fixes this issue. More importantly, I don't understand if it will
> affect our builds in any other way.
>
> I'll see if I can dig out some docs, but if anyone knows in the mean
> time, I'm all ears.
>
I really meant --with-sysroot. That switch is defined in ld's configure,
not the top one.
(it might be better to use --with-sysroot=/, but --with-sysroot
works for me).
It changes the behavior of ld:
from "man ld":
-rpath=dir
Add a directory to the runtime library search path. This is
used
when linking an ELF executable with shared objects. All -rpath
arguments are concatenated and passed to the runtime linker,
which
uses them to locate shared objects at runtime. The -rpath
option
is also used when locating shared objects which are needed by
shared objects explicitly included in the link; see the
description
of the -rpath-link option. If -rpath is not used when
linking an
ELF executable, the contents of the environment variable
"LD_RUN_PATH" will be used if it is defined.
[...]
-rpath-link=dir
When using ELF or SunOS, one shared library may require another.
This happens when an "ld -shared" link includes a shared
library as
one of the input files.
When the linker encounters such a dependency when doing a non-
shared, non-relocatable link, it will automatically try to
locate
the required shared library and include it in the link, if it is
not included explicitly. In such a case, the -rpath-link option
specifies the first set of directories to search. The
-rpath-link
option may specify a sequence of directory names either by
specifying a list of names separated by colons, or by appearing
multiple times.
This option should be used with caution as it overrides the
search
path that may have been hard compiled into a shared library. In
such a case it is possible to use unintentionally a different
search path than the runtime linker would do.
The linker uses the following search paths to locate required
shared libraries:
1. Any directories specified by -rpath-link options.
2. Any directories specified by -rpath options. The difference
between -rpath and -rpath-link is that directories
specified by
-rpath options are included in the executable and used at
runtime, whereas the -rpath-link option is only effective at
link time. Searching -rpath in this way is only supported by
native linkers and cross linkers which have been configured
with the --with-sysroot option.
3. On an ELF system, for native linkers, if the -rpath and
-rpath-link options were not used, search the contents
of the
environment variable "LD_RUN_PATH".
4. On SunOS, if the -rpath option was not used, search any
directories specified using -L options.
5. For a native linker, the search the contents of the
environment
variable "LD_LIBRARY_PATH".
6. For a native ELF linker, the directories in "DT_RUNPATH" or
"DT_RPATH" of a shared library are searched for shared
libraries needed by it. The "DT_RPATH" entries are
ignored if
"DT_RUNPATH" entries exist.
7. The default directories, normally /lib and /usr/lib.
8. For a native linker on an ELF system, if the file
/etc/ld.so.conf exists, the list of directories found in
that
file.
-----------------------------
Conclusion: gcc uses rpath, but rpath is used to search a shared object
required by another one only if the linker has been configured with
--with-sysroot. If nothing else is specified, it uses /etc/ld.so.conf,
which points to the host libraries, and that is the source of the bug.
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