elf: Keep only one '@' for undefined versioned symbols

The symbol string table in the .symtab section is optional and cosmetic.
Keep only one '@' for undefined versioned symbols, which are defined in
shared objects, in the symbol string table.  Update "nm -D" to display
only one '@' for undefined versioned symbols.

bfd/

	PR ld/26382
	* elflink.c (elf_link_output_symstrtab): Keep only one '@' for
	versioned symbols, which are defined in shared objects, in
	symbol string table.

binutils/

	PR ld/26382
	* nm.c (print_symname): Display only one '@' for undefined
	versioned symbols.
	* doc/binutils.texi: Update nm version information.

ld/

	PR ld/26382
	* testsuite/ld-elf/pr26302.nd: Updated.
	* testsuite/ld-elf/pr26302.rd: New file.
	* testsuite/ld-elf/shared.exp: Add a test for readelf -sW.

bfd/ChangeLog

@@ -1,3 +1,10 @@
+2020-08-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26382
+	* elflink.c (elf_link_output_symstrtab): Keep only one '@' for
+	versioned symbols, which are defined in shared objects, in
+	symbol string table.
+
 2020-08-21  Nick Clifton  <nickc@redhat.com>
 
 	* elfnn-aarch64.c (_bfd_aarch64_erratum_835769_scan): Only sort

bfd/elflink.c

@@ -9642,9 +9642,29 @@ elf_link_output_symstrtab (struct elf_final_link_info *flinfo,
     {
       /* Call _bfd_elf_strtab_offset after _bfd_elf_strtab_finalize
 	 to get the final offset for st_name.  */
+      char *versioned_name = (char *) name;
+      if (h != NULL && h->versioned == versioned && h->def_dynamic)
+	{
+	  /* Keep only one '@' for versioned symbols defined in shared
+	     objects.  */
+	  char *version = strrchr (name, ELF_VER_CHR);
+	  char *base_end = strchr (name, ELF_VER_CHR);
+	  if (version != base_end)
+	    {
+	      size_t base_len;
+	      size_t len = strlen (name);
+	      versioned_name = bfd_alloc (flinfo->output_bfd, len);
+	      if (versioned_name == NULL)
+		return 0;
+	      base_len = base_end - name;
+	      memcpy (versioned_name, name, base_len);
+	      memcpy (versioned_name + base_len, version,
+		      len - base_len);
+	    }
+	}
       elfsym->st_name
 	= (unsigned long) _bfd_elf_strtab_add (flinfo->symstrtab,
-					       name, FALSE);
+					       versioned_name, FALSE);
       if (elfsym->st_name == (unsigned long) -1)
 	return 0;
     }

binutils/ChangeLog

@@ -1,3 +1,10 @@
+2020-08-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26382
+	* nm.c (print_symname): Display only one '@' for undefined
+	versioned symbols.
+	* doc/binutils.texi: Update nm version information.
+
 2020-08-21  Mark Wielaard  <mark@klomp.org>
 
 	* testsuite/binutils-all/readelf.exp (readelf_wi_test): Also

binutils/doc/binutils.texi

@@ -924,7 +924,13 @@ The symbol type is unknown, or object file format specific.
 @end table
 
 @item
-The symbol name.
+The symbol name.  If a symbol has version information associated with it,
+then the version information is displayed as well.  If the versioned
+symbol is undefined or hidden from linker, the version string is displayed
+as a suffix to the symbol name, preceded by an @@ character.  For example
+@samp{foo@@VER_1}.  If the version is the default version to be used when
+resolving unversioned references to the symbol, then it is displayed as a
+suffix preceded by two @@ characters.  For example @samp{foo@@@@VER_2}.
 @end itemize
 
 @c man end

binutils/nm.c

@@ -421,7 +421,10 @@ print_symname (const char *form, struct extended_symbol_info *info,
 	= bfd_get_symbol_version_string (abfd, &info->elfinfo->symbol,
 					 FALSE, &hidden);
       if (version_string && version_string[0])
-	printf ("%s%s", hidden ? "@" : "@@", version_string);
+	printf ("%s%s",
+	       (hidden || bfd_is_und_section (info->elfinfo->symbol.section)
+		? "@" : "@@"),
+	       version_string);
     }
 }
 

ld/ChangeLog

@@ -1,3 +1,10 @@
+2020-08-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26382
+	* testsuite/ld-elf/pr26302.nd: Updated.
+	* testsuite/ld-elf/pr26302.rd: New file.
+	* testsuite/ld-elf/shared.exp: Add a test for readelf -sW.
+
 2020-08-20  Nick Clifton  <nickc@redhat.com>
 
 	PR 26428

ld/testsuite/ld-elf/pr26302.nd

@@ -1,3 +1,3 @@
 #...
- +U foo@@FOO
+ +U foo@FOO
 #pass

ld/testsuite/ld-elf/pr26302.rd

@@ -0,0 +1,12 @@
+#...
+Symbol table '\.dynsym' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[a-f0-9]+ +0 +FUNC +GLOBAL +DEFAULT +UND +foo@FOO \([0-9]+\)
+#...
+
+Symbol table '\.symtab' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[a-f0-9]+ +0 +FUNC +GLOBAL +DEFAULT +UND +foo@FOO
+#pass

ld/testsuite/ld-elf/shared.exp

@@ -856,7 +856,8 @@ run_cc_link_tests [list \
 	"-shared -Wl,--no-as-needed tmpdir/pr26302a.so" \
 	"-fPIC" \
 	{pr26302b.c} \
-	{{nm {-u} pr26302.nd} \
+	{{readelf {-sW} pr26302.rd} \
+	 {nm {-u} pr26302.nd} \
 	 {nm {-u -D} pr26302.nd} \
 	 {nm {-u -D --with-symbol-versions} pr26302.nd}} \
 	"pr26302b.so" \