Re: libstdc++ dependency mis-detection in gcc packages?

[Havard Eidnes <he%NetBSD.org@localhost>]

>> For many years I've used this patch which instead only records direct
>> dependencies via DT_NEEDED:
>>
>> https://github.com/TritonDataCenter/pkgsrc/commit/dff5fd726aa1d33966ab4557cc55026f38905f46
>>
>> It might be good to get consensus on this and figure out a portable way
>> to do it for all ELF platforms.

I think on NetBSD (at least from 8 forwards) you dump this info
with "readelf", and the output it produces is a little different
compared to the "elfdump" output.  The attached proof-of-concept
shell script does basically the same operation as the diff using
readelf, it obviously needs to be re-formatted to fit in an .mk
file (and the SYSTEM_DEFAULT_RPATH pasted in instead of the
literal in the example) etc.

We would probably have to add some test to differentiate between
the different systems / tools to get at the direct dependency
information.

In my test case the attached script (which looks at cc1plus from
gcc10) produces the rather un-exciting

/lib/libz.so.1
/lib/libm.so.0
/lib/libc.so.12

output while pointing it at my /usr/pkg/lib/libgs.so produces a
bit more output:

/usr/X11R7/lib/libXt.so.7
/usr/X11R7/lib/libSM.so.7
/usr/X11R7/lib/libICE.so.7
/usr/X11R7/lib/libXext.so.7
/usr/X11R7/lib/libX11.so.7
/usr/pkg/lib/libtiff.so.5
/usr/pkg/lib/libcups.so.2
/usr/pkg/lib/libpng16.so.16
/usr/pkg/lib/libjbig2dec.so.0
/usr/pkg/lib/libjpeg.so.9
/lib/libz.so.1
/usr/pkg/lib/liblcms2.so.2
/lib/libm.so.0
/usr/pkg/lib/libidn.so.12
/usr/pkg/lib/libpaper.so.1
/usr/X11R7/lib/libfontconfig.so.2
/usr/X11R7/lib/libfreetype.so.19
/usr/lib/libbz2.so.1
/usr/pkg/lib/libopenjp2.so.7
/lib/libpthread.so.1
/lib/libc.so.12

while ldd on the latter produces no less than 52 lines of output.


However...  While the above is probably a good idea, this doesn't
fully explain why libstdc++.so.7 is in the "required" list of the
gcc10 or gcc12 binary packages.  gcc10 only depends on gsed, and
none of the binaries in the gcc10 package appear to depend on
libstdc++.so.7, judging by ldd output on the /bin/ and /libexec/
files in that package.


Regards,

- Håvard

#! /bin/sh

PKGSRC_SETENV=""
bins="/usr/pkg/gcc10/libexec/gcc/x86_64--netbsd/10.4.0/cc1plus"
libs=""
AWK=awk
SED=sed
DESTDIR=""
SORT=sort
SYSTEM_DEFAULT_RPATH="/lib:/usr/lib"

# requires=`
(${PKGSRC_SETENV} readelf -d $bins $libs 2>/dev/null || true) | ${AWK} '
        /NEEDED/ {
                l = gensub(/.*\[/, "", 0);
                lib = gensub(/\]/, "", 0, l);
                dsolibs = dsolibs (dsolibs ? ":" : "") lib;
        }
        /RPATH/ {
                l = gensub(/.*\[/, "", 0);
                path = gensub(/\]/, "", 0, l);
                nrpath = split(path ":/lib:/usr/lib", rpath, ":");
                nlibs = split(dsolibs, libs, ":");
                for (l = 1; l <= nlibs; l++) {
                        for (r = 1; r <= nrpath; r++) {
                                sub(/\/$/, "", rpath[r]);
                                libfile = rpath[r] "/" libs[l];
                                if (!(libfile in libcache)) {
                                        libcache[libfile] = system("test -f " libfile);
                                }
                                if (libcache[libfile] == 0) {
                                        print libfile;
                                        break;
                                }
                        }
                }

        }
        '


# | ${SED} -e "s,${DESTDIR},," | ${SORT} -u`;

# echo $requires