Guido U. Draheim <firstname.lastname@example.org>
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cryp.to ac-archive's C Support (released)
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).
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
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.
this ac-macro is trying to detect a valid HOST_CC which is not a
cross-compiler. This is done by looking into the $PATH for a "cc"
and the result is patched into libtool a HOST_CC, iow it adds
another configured variable at the top of the libtool script.
In discussions on the libtool mailinglist it occurred that later
gcc/binutils generations are able to link with dlls directly, i.e.
there is no import-lib needed anymore. The import-table is created
within the linker itself (in-memory) and bound to the .exe/.dll
currently in the making. The whole stuff of impgen exe and
compiling it on-the-fly, well, it is superflouos then.
Since mingw crosscompilers tend to be quite a fresh development it
was agreed to remove the impgen stuff completly from libtool
sources. Still however, this macro does not hurt since it does not
patch impgen cmds but it just adds HOST_CC which might be useful in
other cross-compiling cases as well. Therefore, you can leave it in
for maximum compatibility and portability.
[# patch libtool to add HOST_CC sometimes needed in crosscompiling a win32 dll
if grep "HOST_CC" libtool >/dev/null; then
if test "$build" != "$host" ; then
if test "_$HOST_CC" = "_" ; then
for i in `echo $PATH | sed 's,:, ,g'` ; do
test -x $i/cc && HOST_CC=$i/cc
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