abi: explicitly export intended symbols and hide others

This adds all exported symbols in the map files explicitly under
the following rules:
 - Symbols mentioned in internal headers go in a section which is
   valid only for testing, and linking with these symbols will break
   in library updates.
 - Symbols mentioned in installed headers go in the exported sections
   and are considered part of the ABI.
 - All internal symbols move to internal headers.
 - The _nettle_md5_compress and _nettle_sha1_compress become exported
   without the _nettle prefix, due to existing usage.

1 files changed, 11 insertions, 2 deletions

diff --git a/libnettle.map.in b/libnettle.map.in
index 02455bc5..95557217 100644
--- a/libnettle.map.in
+++ b/libnettle.map.in
@@ -1,4 +1,4 @@
-# libnettle.map -- libnettle linker version script.           -*- ld-script -*-
+# libnettle.map.in -- linker version script.           -*- ld-script -*-
 
 #
 # The symbol version must be updated on every nettle
@@ -9,9 +9,18 @@ NETTLE_@LIBNETTLE_MAJOR@
 {
   global:
     nettle_*;
-    _nettle_*;
 
   local:
     *;
 };
 
+# Internal symbols which are to be used only for unit or other
+# testing. Compatibility may break across releases.
+NETTLE_INTERNAL_@LIBNETTLE_MAJOR@_@LIBNETTLE_MINOR@
+{
+  global:
+    _nettle_*;
+
+  local:
+    *;
+};