Fix case where IR file provides symbol visibility but replacement file does not.

In PR 22868, two IR files provide conflicting visibility for a symbol.
When a def with PROTECTED visibility is seen after a def with DEFAULT
visibility, gold does not override the visibility. Later, if the
replacement object define the symbol with DEFAULT visibility, the symbol
remains DEFAULT. This was caused by a recent change to allow multiply-defined
absolute symbols, combined with the fact that the plugin framework was using
SHN_ABS as the section index for placeholder symbols. The solution is to
use a real (but arbitrary) section index.

gold/
	PR gold/22868
	* plugin.cc (Sized_pluginobj::do_add_symbols): Use a real section
	index instead of SHN_ABS for defined symbols.
	* testsuite/Makefile.am (plugin_pr22868): New test case.
	* testsuite/Makefile.in: Regenerate
	* testsuite/plugin_pr22868.sh: New test script.
	* testsuite/plugin_pr22868_a.c: New source file.
	* testsuite/plugin_pr22868_b.c: New source file.

1 files changed, 2 insertions, 1 deletions

diff --git a/gold/plugin.cc b/gold/plugin.cc
index c921f7c..3415b91 100644
--- a/gold/plugin.cc
+++ b/gold/plugin.cc
@@ -1424,7 +1424,8 @@ Sized_pluginobj<size, big_endian>::do_add_symbols(Symbol_table* symtab,
         {
         case LDPK_DEF:
         case LDPK_WEAKDEF:
-          shndx = elfcpp::SHN_ABS;
+          // We use an arbitrary section number for a defined symbol.
+          shndx = 1;
           break;
         case LDPK_COMMON:
           shndx = elfcpp::SHN_COMMON;