Expand comments in elf/ldconfig.c (search_dir)

[platform/upstream/glibc.git] / elf / ldconfig.c

diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index 4211f4c..2d9c780 100644 (file)
--- 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)