From 97114a383fc167a64b0c85c9c5eaeb4f3ecd28f9 Mon Sep 17 00:00:00 2001 From: Carlos O'Donell Date: Sat, 29 Nov 2014 01:04:57 -0500 Subject: [PATCH] Expand comments in elf/ldconfig.c (search_dir) Developers creating development packages must take care to have their static linker DSO link point to the actual SONAME file. This allows ldconfig to correctly create the required links for the SONAME. The behaviour is now more clearly documented in a code comment added by this patch. --- ChangeLog | 4 ++++ elf/ldconfig.c | 26 ++++++++++++++++++++++++-- 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index 8a6e89e48e..39e70e130c 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,7 @@ +2014-11-29 Carlos O'Donell + + * elf/ldconfig.c (search_dir): Expand comment. + 2014-11-29 Joseph Myers * conform/Makefile (linknamespace-symlist-stdlibs-base): New diff --git a/elf/ldconfig.c b/elf/ldconfig.c index 4211f4c9cf..2d9c780d22 100644 --- a/elf/ldconfig.c +++ b/elf/ldconfig.c @@ -893,8 +893,30 @@ search_dir (const struct dir_entry *entry) /* A link may just point to itself. */ if (is_link) { - /* If the path the link points to isn't its soname and it is not - .so symlink for ld(1) only, we treat it as a normal file. */ + /* If the path the link points to isn't its soname or it is not + the .so symlink for ld(1), we treat it as a normal file. + + You should always do this: + + libfoo.so -> SONAME -> Arbitrary package-chosen name. + + e.g. libfoo.so -> libfoo.so.1 -> libfooimp.so.9.99. + Given a SONAME of libfoo.so.1. + + You should *never* do this: + + libfoo.so -> libfooimp.so.9.99 + + If you do, and your SONAME is libfoo.so.1, then libfoo.so + fails to point at the SONAME. In that case ldconfig may consider + libfoo.so as another implementation of SONAME and will create + symlinks against it causing problems when you try to upgrade + or downgrade. The problems will arise because ldconfig will, + depending on directory ordering, creat symlinks against libfoo.so + e.g. libfoo.so.1.2 -> libfoo.so, but when libfoo.so is removed + (typically by the removal of a development pacakge not required + for the runtime) it will break the libfoo.so.1.2 symlink and the + application will fail to start. */ const char *real_base_name = basename (real_file_name); if (strcmp (real_base_name, soname) != 0)