Re: [PATCH] libstdc++: Fix error shown during Solaris build

[Iain Sandoe <idsandoe@googlemail.com>]

Jonathan Wakely <jwakely@redhat.com> wrote:

> On 13/11/20 11:07 +0000, Jonathan Wakely wrote:
>> Currently this is shown when building libstdc++ on Solaris:
>>
>> -lrt: open: No such file or directory
>>
>> The error comes from the make_sunver.pl script which tries to open each
>> of its arguments. The arguments are passed by this make rule:
>>
>> 	perl ${glibcxx_srcdir}/scripts/make_exports.pl \
>> 	  libstdc++-symbols.ver \
>> 	  $(libstdc___la_OBJECTS:%.lo=.libs/%.o) \
>> 	 `echo $(libstdc___la_LIBADD) | \
>> 	    sed 's,/\([^/.]*\)\.la,/.libs/\1.a,g'` \
>> 	 > $@ || (rm -f $@ ; exit 1)
>>
>> The $(libstdc___la_LIBADD) variable includes $(GLIBCXX_LIBS) which
>> contains -lrt on Solaris.
>>
>> This patch adds another sed script to filter -l arguments from the echo
>> command. In order to reliably match ' -l[^ ]* ' the echo arguments are
>> quoted and a space added before and after them. This might be overkill
>> just to remove -lrt from the start of the string, but should be robust
>> in case other -l arguments are added to $(GLIBCXX_LIBS), or in case the
>> $(libstdc___la_LIBADD) libraries are reordered.
>>
>> libstdc++-v3/ChangeLog:
>>
>> 	* src/Makefile.am (libstdc++-symbols.ver-sun): Remove -lrt from
>> 	arguments passed to make_sunver.pl script.
>> 	* src/Makefile.in: Regenerate.
>>
>> Tested sparc-solaris2.11. Rainer, does this look OK?
>>
>> Iain, the libstdc++-symbols.explist target for Darwin is very similar,
>> but I don't know if it's a problem there. Does GLIBCXX_LIBS contain
>> anything in $target/libstdc++-v3/src/Makefile on Darwin?
>>
>> Should we make the same change just in case?
>
> On examining acinclude.m4 it looks like GLIBCXX_LIBS could in theory
> be non-empty for any target, including Darwin:
>
>  elif test x"$enable_libstdcxx_time" != x"no"; then
>
>    if test x"$enable_libstdcxx_time" = x"rt"; then
>      AC_SEARCH_LIBS(clock_gettime, [rt posix4])
>      AC_SEARCH_LIBS(nanosleep, [rt posix4])
>    else
>      AC_SEARCH_LIBS(clock_gettime, [posix4])
>      AC_SEARCH_LIBS(nanosleep, [posix4])
>    fi
>
>    case "$ac_cv_search_clock_gettime" in
>      -l*) GLIBCXX_LIBS=$ac_cv_search_clock_gettime
>      ;;
>    esac
>    case "$ac_cv_search_nanosleep" in
>      -l*) GLIBCXX_LIBS="$GLIBCXX_LIBS $ac_cv_search_nanosleep"
>      ;;
>    esac
>
>    AC_SEARCH_LIBS(sched_yield, [rt posix4])
>
>    case "$ac_cv_search_sched_yield" in
>      -lposix4*)
>      GLIBCXX_LIBS="$GLIBCXX_LIBS $ac_cv_search_sched_yield"
>      ac_has_sched_yield=yes
>      ;;
>      -lrt*)
>      if test x"$enable_libstdcxx_time" = x"rt"; then
> 	GLIBCXX_LIBS="$GLIBCXX_LIBS $ac_cv_search_sched_yield"
>        ac_has_sched_yield=yes
>      fi
>      ;;
>      *)
>      ac_has_sched_yield=yes
>      ;;
>    esac
>
> But in practice the snippet above is only used if you explicitly
> configure with --enable-libstdcxx-time={yes,rt} and will only add
> anything to GLIBCXX_LIBS if clock_gettime or nanosleep lives in one of
> librt or libposix4. I think libposix4 is Solaris-specific, and I don't
> think Darwin has librt. So in practice I don't think there's a
> problem on Darwin today.

Agreed, neither of those libs is currently in use on Darwin.

There have, in some cases, been library entries that are simply a symlink to
the one providing the equivalent functionality, to minimize cross-platform  
build
hassles - but I see no entry for librt.dylib or posix4.

thanks
Iain