wafsamba/samba_abi: always hide ABI symbols which must be local

binutils 2.31 is going to change how shared libraries are linked, such
that they always provide their own local definitions of the _end, _edata
and _bss_start symbols.  This would all be fine, except for shared
libraries that export all symbols be default.  (Rather than just
exporting those symbols that form part of their API).

According to binutils developers, we should only export the symbols we
explicitly want to be used. We don't use this principle for all our
libraries and deliberately don't want to have ABI versioning control for
all of them, so the change I introduce here is to explicitly mark those
symbols that will always be added by default linker configuration with
binutils 2.31 as local. Right now these are '_end', '_edata', and
'__bss_start' symbols.

Signed-off-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Jul 13 17:45:36 CEST 2018 on sn-devel-144

diff --git a/buildtools/wafsamba/samba_abi.py b/buildtools/wafsamba/samba_abi.py
index 196b468f5b35f096f34dfa6e454f38e00a84ccbe..4603e764feafe79aacf23604026b8f1073d9a2ea 100644 (file)
--- a/buildtools/wafsamba/samba_abi.py
+++ b/buildtools/wafsamba/samba_abi.py
@@ -192,10 +192,12 @@ def abi_write_vscript(f, libname, current_version, versions, symmap, abi_match):
             f.write("\t\t%s;\n" % x)
     else:
         f.write("\t\t*;\n")
-    if abi_match != ["*"]:
-        f.write("\tlocal:\n")
-        for x in local_abi:
-            f.write("\t\t%s;\n" % x[1:])
+    # Always hide symbols that must be local if exist
+    local_abi.extend(["!_end", "!__bss_start", "!_edata"])
+    f.write("\tlocal:\n")
+    for x in local_abi:
+        f.write("\t\t%s;\n" % x[1:])
+    if global_abi != ["*"]:
         if len(global_abi) > 0:
             f.write("\t\t*;\n")
     f.write("};\n")

diff --git a/buildtools/wafsamba/tests/test_abi.py b/buildtools/wafsamba/tests/test_abi.py
index bba78c1ba0745b37a59a50ee71d9c31b0c63ae7d..7489214699064f865802f3f2ef7cd4d4b71b2cd5 100644 (file)
--- a/buildtools/wafsamba/tests/test_abi.py
+++ b/buildtools/wafsamba/tests/test_abi.py
@@ -66,6 +66,10 @@ class WriteVscriptTests(TestCase):
 1.0 {
 \tglobal:
 \t\t*;
+\tlocal:
+\t\t_end;
+\t\t__bss_start;
+\t\t_edata;
 };
 """)
 
@@ -84,6 +88,10 @@ MYLIB_0.1 {
 1.0 {
 \tglobal:
 \t\t*;
+\tlocal:
+\t\t_end;
+\t\t__bss_start;
+\t\t_edata;
 };
 """)
 
@@ -99,6 +107,9 @@ MYLIB_0.1 {
 \t\t*;
 \tlocal:
 \t\texc_*;
+\t\t_end;
+\t\t__bss_start;
+\t\t_edata;
 };
 """)
 
@@ -115,6 +126,9 @@ MYLIB_0.1 {
 \t\tpub_*;
 \tlocal:
 \t\texc_*;
+\t\t_end;
+\t\t__bss_start;
+\t\t_edata;
 \t\t*;
 };
 """)