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On 29.04.2014 14:34, YIRAN LI wrote:
> Hi friends,
>
> I'm now moving my ffmpeg build from MinGW to Mingw-w64 because the latter
> supports delay load. To be a bit more specific, ffmpeg could dynamically
> link to many external libraries, but I want these external libs be
> downloaded and used only when they are used (functions called).
>
> For example, there'a libspeex for which I configured with ./configure
> --enable-static=no --prefix=/mingw, so these files are generated
> libspeex-1.dll, libspeex.dll.a libspeex.la.
>
> According to this article
> http://mingw-users.1079350.n2.nabble.com/Delayloading-windows-
> libraries-Finally-the-real-deal-td7472183.html,
>
> what I need to do is:
>
> 1. gendef libspeex-1.dll to get the libspeex-1.def 2. dlltool --def
> libspeex-1.def --output-delaylib libspeex.dll.a
>
> so the old libspeex.dll.a is replaced by the newly generated one, and
> 'make install' will install header files and all lib files into mingw
> folder.
A more elegant (or braindead, YMMV) solution is to hack configure.ac of the
package in question and add this for *-*-mingw* hosts:
archive_cmds='$CC -shared $libobjs $deplibs $compiler_flags -o
$output_objdir/$soname ${wl}--enable-auto-image-base -Xlinker --output-def
- -Xlinker $lib.def && $DLLTOOL --dllname $soname --def $lib.def
- --output-delaylib $lib'
# If the export-symbols file already is a .def file (1st line
# is EXPORTS), use it as is; otherwise, prepend...
archive_expsym_cmds='if test "x`$SED 1q $export_symbols`" = xEXPORTS; then
cp $export_symbols $output_objdir/$soname.def;
else
echo EXPORTS > $output_objdir/$soname.def;
cat $export_symbols >> $output_objdir/$soname.def;
fi~
$CC -shared $output_objdir/$soname.def $libobjs $deplibs $compiler_flags -o
$output_objdir/$soname ${wl}--enable-auto-image-base;
$DLLTOOL --dllname $soname --def $output_objdir/$soname.def --output-delaylib
$lib'
This code is a verbatim copy of libtool that is patched to create a
delay-load import library instead of the normal import library. This takes
advantage of the fact that libtool does have a .def file at hand already, and
thus there's no need to call gendef.
>
> But what I want to know is, what's the libspeex.la ? Should I also
> regenerate it or just install the old ones?
.la files are libtool helpers.
IMO they are useful (roughly as useful as libtool itself) when you build a
package, and Makefile.am files SHOULD refer to .la files by name when needing
to link to a library produced within the same package.
However, they are a hindrance when linking package libraries from outside (as
they remember all kinds of nasty details, absolute paths and such). Therefore
i strongly recommend against installing .la files (i routinely purge anything
a package installs, looking for .la files and deleting them with extreme
prejudice). dll.a import (with or without delay-loading) libraries in
/mingw/lib should be enough (and for anything more complex there's pkgconfig).
- --
O< ascii ribbon - stop html email! - www.asciiribbon.org
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