Bruno Haible <[EMAIL PROTECTED]> writes:
> The problem is brought in by the fact that we build a single libgnulib or
> libcoreutils for all executables of a package, and if a single function
> in this library needs, say, high-resolution timers, the libgnulib or
> libcoreutils has "-lrt" in its link specification.
That's what leads to the problem here, but the problem can occur even
if we don't build a libgnulib. For example, a package might not need
any gnulib .o files at all, but it still might invoke something like
gl_CLOCK_TIME, which merely sets LIB_CLOCK_GETTIME=-lrt and defines
HAVE_CLOCK_GETTIME. If a package like that defines several programs,
only some of which call clock_gettime, then the maintainer will have
to do something like this (this is an extract from
coreutils/src/Makefile.am):
pr_LDADD = $(LDADD) $(LIB_CLOCK_GETTIME)
shred_LDADD = $(LDADD) $(LIB_GETHRXTIME) $(LIB_FDATASYNC)
sort_LDADD = $(LDADD) $(POW_LIB) $(LIB_GETHRXTIME)
...
where each program is carefully linked to each optionally-available
library it might use.
This sort of cataloging is error-prone and a pain to maintain. It
should be automated, and -zignore does the automation. (I don't know
why -zignore is not the default; but it isn't and we have to deal with
it.)
> This uses 'ldd'. This command is OS dependent:
>
> AIX: dump -H
> IRIX: elfdump -Dl
> HP-UX: chatr
> OSF/1, Tru64: odump -Dl
> Solaris: ldd
> glibc-based: ldd
Now that you mention it, there's also 'otool -L' on Mac OS X.
However, does the problem occur with the linkers used on AIX, IRIX,
HP-UX, OSF/1, and Tru64? If not, then I'm not sure it's worth trying
all the possibilities. But if so, I suppose we could install a
further patch that looks something like the following. But this
raises Ralf Wildenhues's point: do these other linkers need some other
option, one that isn't spelled "-zignore"?
--- lib-ignore.m4.~1.1.~ 2006-01-09 10:42:51.000000000 -0800
+++ lib-ignore.m4 2006-01-11 10:08:27.000000000 -0800
@@ -13,21 +13,29 @@ AC_DEFUN([gl_IGNORE_UNUSED_LIBRARIES],
[gl_cv_ignore_unused_libraries],
[gl_cv_ignore_unused_libraries=none
AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [gl_ldd_output0=`(ldd conftest$ac_exeext) 2>/dev/null` ||
- gl_ldd_output0=])
+ [for gl_ldd in \
+ ldd \
+ 'chatr' \
+ 'dump -H' \
+ 'elfdump -Dl' \
+ 'odump -Dl' \
+ 'otool -L' \
+ :; do
+ gl_ldd_output0=`($gl_ldd conftest$ac_exeext) 2>/dev/null` && break
+ done])
if test "$gl_ldd_output0"; then
gl_saved_ldflags=$LDFLAGS
gl_saved_libs=$LIBS
LIBS="$LIBS -lm"
AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [gl_ldd_output1=`(ldd conftest$ac_exeext) 2>/dev/null` ||
+ [gl_ldd_output1=`($gl_ldd conftest$ac_exeext) 2>/dev/null` ||
gl_ldd_output1=])
if test "$gl_ldd_output1" && test "$gl_ldd_output0" != "$gl_ldd_output1"
then
for gl_flags in '-Xlinker -zignore' '-zignore'; do
LDFLAGS="$gl_flags $LDFLAGS"
AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [if gl_ldd_output2=`(ldd conftest$ac_exeext) 2>/dev/null` &&
+ [if gl_ldd_output2=`($gl_ldd conftest$ac_exeext) 2>/dev/null` &&
test "$gl_ldd_output0" = "$gl_ldd_output2"; then
gl_cv_ignore_unused_libraries=$gl_flags
fi])
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