Very Computer

by **Davi** » Wed, 10 Nov 1999 04:00:00

I know FreeBSD has dlopen(), dlsym(), etc... but will it ever have
libdl or at least a port of it?

Thanks
David

by **Chris Costell** » Thu, 11 Nov 1999 04:00:00

> I know FreeBSD has dlopen(), dlsym(), etc... but will it ever have
> libdl or at least a port of it?

Just write a library with weak symbols for them.

Compile this C source into a library.

------ (begin) ------
void *dlopen(const char *, int);
void *dlsym(void *, const char *);
const char *dlerror(void);
int dlclose(void *handle);
------- (end) -------

Though I don't see why you need it.

by **Donn Mille** » Thu, 11 Nov 1999 04:00:00

> I know FreeBSD has dlopen(), dlsym(), etc... but will it ever have
> libdl or at least a port of it?

Very good point. I know our -lc (libc) has these functions, but
you make a good point in having these extricated into a libdl.
However, the only good this may do is compatibility with Linux's
dlopen(), which on Linux resides in -libdl. You may want to bring

--
- Donn

by **Chris Costell** » Thu, 11 Nov 1999 04:00:00

> Very good point. I know our -lc (libc) has these functions, but
> you make a good point in having these extricated into a libdl.
> However, the only good this may do is compatibility with Linux's
> dlopen(), which on Linux resides in -libdl. You may want to bring

See my previous post. There's no need to bloat our source
tree any more with that sort of thing, in my opinion.

by **Jan Andre** » Thu, 11 Nov 1999 04:00:00

> > I know FreeBSD has dlopen(), dlsym(), etc... but will it ever have
> > libdl or at least a port of it?

> Just write a library with weak symbols for them.

> Compile this C source into a library.

> ------ (begin) ------
> void *dlopen(const char *, int);
> void *dlsym(void *, const char *);
> const char *dlerror(void);
> int dlclose(void *handle);
> ------- (end) -------

> Though I don't see why you need it.

Good point. Why not just:

# cd /usr/local/lib
# gcc -shared -Wl,-soname,libdl.so.1 -o libdl.so.1 -x c /dev/null
# ln -s libdl.so.1 libdl.so

Why you would need this? Well, there are some bloated autoconf scripts
which test for a particular feature which is present in a FreeBSD
system, but try to link their test binary against -ldl and so fail.
This is, of course, not a solution, but a good bug-compatibility
`feature' IMO.

--

"Bell Labs Unix -- reach out and grep someone."

by **Chris Costell** » Fri, 12 Nov 1999 04:00:00

> Good point. Why not just:

...

Quote:> Why you would need this? Well, there are some bloated autoconf scripts
> which test for a particular feature which is present in a FreeBSD
> system, but try to link their test binary against -ldl and so fail.
> This is, of course, not a solution, but a good bug-compatibility
> `feature' IMO.

I don't understand (nor do I want to understand) autoconf. I
assumed the way autoconf searches for a function in a library is
by looking at the symbols (man nm).

by **Paul Southwor** » Fri, 12 Nov 1999 04:00:00

Quote:>> Why you would need this? Well, there are some bloated autoconf scripts
>> which test for a particular feature which is present in a FreeBSD
>> system, but try to link their test binary against -ldl and so fail.

That is not a smart test. That is not the fault of autoconf.

Quote:>> This is, of course, not a solution, but a good bug-compatibility
>> `feature' IMO.

> I don't understand (nor do I want to understand) autoconf. I
>assumed the way autoconf searches for a function in a library is
>by looking at the symbols (man nm).

autoconf lets you roll up just about any test you want. In general,
functions are tested by using them - compiling a code snippet and
linking with specific libraries. This allows you to also test whether
the function takes the number and type of arguments you expect.

I am not a particular fan of autoconf, but like most tools, it should
probably be seen as a length of rope. If someone writes a bad autoconf
script which is not portable, the rest of the world should not alter
their operating systems to fit.

--Paul

by **Donn Mille** » Sat, 13 Nov 1999 04:00:00

> Why you would need this? Well, there are some bloated autoconf scripts
> which test for a particular feature which is present in a FreeBSD
> system, but try to link their test binary against -ldl and so fail.
> This is, of course, not a solution, but a good bug-compatibility
> `feature' IMO.

I don't think it's necessary. I find it easier to just have the
autoconf package installed, and modify configure.in. There, you
can pretty much change all occurrences of -ldl to -lc by hand,
and then run autoconf. Or, if configure.in isn't present, just
modify configure.

--
- Donn

by **Jan Andre** » Sat, 13 Nov 1999 04:00:00

> # cd /usr/local/lib
> # gcc -shared -Wl,-soname,libdl.so.1 -o libdl.so.1 -x c /dev/null
> # ln -s libdl.so.1 libdl.so

Or just,

# ar r /usr/local/lib/libdl.a

Who wants an empty library to be linked dynamically? ;-)

--

"Bell Labs Unix -- reach out and grep someone."

by **Jan Andre** » Sat, 13 Nov 1999 04:00:00

> >> Why you would need this? Well, there are some bloated autoconf scripts
> >> which test for a particular feature which is present in a FreeBSD
> >> system, but try to link their test binary against -ldl and so fail.

> That is not a smart test. That is not the fault of autoconf.

You misunderstood me. I know you can write quite smart tests with
autoconf, but some people are actually writing dumb tests, and instead
of fixing them (which can be annoying if they don't include
configure.in), you can create an empty library and it'll just work.

Quote:> >> This is, of course, not a solution, but a good bug-compatibility
> >> `feature' IMO.

> > I don't understand (nor do I want to understand) autoconf. I
> >assumed the way autoconf searches for a function in a library is
> >by looking at the symbols (man nm).

> autoconf lets you roll up just about any test you want. In general,
> functions are tested by using them - compiling a code snippet and
> linking with specific libraries. This allows you to also test whether
> the function takes the number and type of arguments you expect.

> I am not a particular fan of autoconf, but like most tools, it should
> probably be seen as a length of rope. If someone writes a bad autoconf
> script which is not portable, the rest of the world should not alter
> their operating systems to fit.

I wasn't talking about extending FreeBSD by an empty libdl. ;-) I just
wanted to point to an easy way of making these dumb tests work.

Btw, is -ldl a very Linux specific feature? Or are there many other
OSes that also habe a libdl?

--

"Bell Labs Unix -- reach out and grep someone."

by **Patrick TJ McPh** » Sun, 14 Nov 1999 04:00:00

% Btw, is -ldl a very Linux specific feature? Or are there many other
% OSes that also habe a libdl?

There are other OSes which also have libdl.
--

Patrick TJ McPhee
East York Canada

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