l...@gnu.org (Ludovic Courtès) skribis: > As Andy just noted on IRC, shared library lookup is inefficient in Guix, > because there’s one entry per library in RUNPATH. So we get: > > open("/gnu/store/y8ppqsxiki39n4mqpb4mab6bgwqsnnp7-libgc-7.4.2/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) > open("/gnu/store/w0bkj9qh7iqcklm5ld8ghg1ynnzqyv00-libffi-3.2.1/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) > open("/gnu/store/d5gw4i6bnyznmbr55ba39bl3pgrhsyp0-libunistring-0.9.6/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) > open("/gnu/store/6k08nkddnrb15h5pwp1s0fa94mr1qas9-gmp-6.1.1/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) > open("/gnu/store/9yn89bkl8vcg5rh9dmw3jijciwgrwjls-libltdl-2.4.6/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) > open("/gnu/store/iwgi9001dmmihrjg4rqhd6pa6788prjw-glibc-2.24/lib/libm.so.6", > O_RDONLY|O_CLOEXEC) = 3 > > An alternate approach would be for ld-wrapper to replace “-lfoo” with > “/gnu/store/…/libfoo.so”, which would add the absolute file name as > NEEDed in the ELF file.
This is actually impossible, as discussed at <https://lists.gnu.org/archive/html/guix-devel/2017-09/msg00075.html>: Per the ELF v1.2 spec¹ (page 82), setting DT_NEEDED to an absolute file name would prevent overriding via LD_LIBRARY_PATH, which is not desirable. It turns out we cannot even set DT_NEEDED to an absolute file name in the first place, because ld records the DT_SONAME of the library, when it’s available (which is the case most of the time), rather than its file name. ¹ http://refspecs.linuxbase.org/elf/elf.pdf Ludo’.