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Autoconf Macro: patch_libtool_to_add_host_cc
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<h1>
patch_libtool_to_add_host_cc
</h1>
<h2>
Synopsis
</h2>
<p class="indent" style="white-space:nowrap;">
<code>PATCH_LIBTOOL_TO_ADD_HOST_CC</code>
</p>
<h2>
Description
</h2>
<div class="indent">
<p>
The libtool 1.4.x processing (and patched 1.3.5) uses a little "impgen"
tool to turn a "*.dll" into an import "*.lib" as it is needed for win32
targets. However, this little tool is not shipped by binutils, it is not
even a command option of dlltool or dllwrap. It happens to be a C source
snippet implanted into the libtool sources - it gets written to ".libs",
compiled into a binary on-the-fly, and executed right away on the "dll"
file to create the import-lib (dll.a files in gcc-speak).
</p>
<p>
This mode works fine for a native build within mingw or cygwin, but it does
not work in cross-compile mode since CC is a crosscompiler - it will create
an .exe file on a non-win32 system, and as a result an impgen.exe is
created on-the-fly that can not be executed on-the-fly. Luckily, the actual
libtool snippet uses HOST_CC to compile the sources which has a fallback to
CC when the HOST_CC variable was not set.
</p>
<p>
this ac-macro is trying to detect a valid HOST_CC which is not a
cross-compiler. This is done by looking into the $PATH for a "cc" and the
result is patched into libtool a HOST_CC, iow it adds another configured
variable at the top of the libtool script.
</p>
<p>
In discussions on the libtool mailinglist it occurred that later
gcc/binutils generations are able to link with dlls directly, i.e. there is
no import-lib needed anymore. The import-table is created within the linker
itself (in-memory) and bound to the .exe/.dll currently in the making. The
whole stuff of impgen exe and compiling it on-the-fly, well, it is
superflouos then.
</p>
<p>
Since mingw crosscompilers tend to be quite a fresh development it was
agreed to remove the impgen stuff completly from libtool sources. Still
however, this macro does not hurt since it does not patch impgen cmds but
it just adds HOST_CC which might be useful in other cross-compiling cases
as well. Therefore, you can leave it in for maximum compatibility and
portability.
</p>
</div>
<h2>
Author
</h2>
<p class="indent">
Guido Draheim <guidod@gmx.de>
</p>
<h2>
Last Modified
</h2>
<p class="indent">
2005-01-21
</p>
<h2>
M4 Source Code
</h2>
<div class="indent">
<pre class="m4source">
AC_DEFUN([PATCH_LIBTOOL_TO_ADD_HOST_CC],
[# patch libtool to add HOST_CC sometimes needed in crosscompiling a win32 dll
if grep "HOST_CC" libtool >/dev/null; then
if test "$build" != "$host" ; then
if test "_$HOST_CC" = "_" ; then
HOST_CC="false"
for i in `echo $PATH | sed 's,:, ,g'` ; do
test -x $i/cc && HOST_CC=$i/cc
done
fi
AC_MSG_RESULT(patching libtool to add HOST_CC=$HOST_CC)
test -f libtool.old || (mv libtool libtool.old && cp libtool.old libtool)
sed -e "/BEGIN.*LIBTOOL.*CONFIG/a\\
HOST_CC=$HOST_CC" libtool >libtool.new
(test -s libtool.new || rm libtool.new) 2>/dev/null
test -f libtool.new && mv libtool.new libtool # not 2>/dev/null !!
test -f libtool || mv libtool.old libtool
fi
fi
])
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