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Drop undefined local symbols from symtab?

From: Alan Modra <amodra at gmail dot com>
To: binutils at sourceware dot org
Date: Wed, 18 Feb 2015 21:57:16 +1030
Subject: Drop undefined local symbols from symtab?
Authentication-results: sourceware.org; auth=none
Does anyone see any harm in dropping undefined local symbols from
.symtab?  I've been meaning to do this for a while, mainly to get rid
of undefined ppc64 "dot-symbols".

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 44fc2bb..138c4ba 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,8 @@
+2015-02-18  Alan Modra  <amodra@gmail.com>
+
+	* elflink.c (elf_link_input_bfd): Drop undefined local syms.
+	(elf_link_output_extsym): Likewise.  Tidy.  Expand comment.
+
 2015-02-17  Alan Modra  <amodra@gmail.com>
 
 	PR ld/17975
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 038e43d..f4c5398 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -8902,8 +8902,9 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
      a regular file, or that we have been told to strip.  However, if
      h->indx is set to -2, the symbol is used by a reloc and we must
      output it.  */
+  strip = FALSE;
   if (h->indx == -2)
-    strip = FALSE;
+    ;
   else if ((h->def_dynamic
 	    || h->ref_dynamic
 	    || h->root.type == bfd_link_hash_new)
@@ -8929,12 +8930,11 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 	   && h->root.u.undef.abfd != NULL
 	   && (h->root.u.undef.abfd->flags & BFD_PLUGIN) != 0)
     strip = TRUE;
-  else
-    strip = FALSE;
 
   /* If we're stripping it, and it's not a dynamic symbol, there's
-     nothing else to do unless it is a forced local symbol or a
-     STT_GNU_IFUNC symbol.  */
+     nothing else to do.   However, if it is a forced local symbol or
+     an ifunc symbol we need to give the backend finish_dynamic_symbol
+     function a chance to make it dynamic.  */
   if (strip
       && h->dynindx == -1
       && h->type != STT_GNU_IFUNC
@@ -9207,7 +9207,13 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 
   /* If we're stripping it, then it was just a dynamic symbol, and
      there's nothing else to do.  */
-  if (strip || (input_sec->flags & SEC_EXCLUDE) != 0)
+  if (strip)
+    return TRUE;
+  if ((input_sec->flags & SEC_EXCLUDE) != 0)
+    return TRUE;
+  if (input_sec == bfd_und_section_ptr
+      && !h->root.linker_def
+      && ELF_ST_BIND (sym.st_info) == STB_LOCAL)
     return TRUE;
 
   /* Output a FILE symbol so that following locals are not associated
@@ -9455,8 +9461,9 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 
       *ppsection = isec;
 
-      /* Don't output the first, undefined, symbol.  */
-      if (ppsection == flinfo->sections)
+      /* Don't output the first, undefined, symbol.  In fact, don't
+	 output any undefined local symbol.  */
+      if (isec == bfd_und_section_ptr)
 	continue;
 
       if (ELF_ST_TYPE (isym->st_info) == STT_SECTION)
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 43cf4e8..41b37af 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,8 @@
+2015-02-18  Alan Modra  <amodra@gmail.com>
+
+	* emultempl/elf32.em (gld${EMULATION_NAME}_before_allocation): Set
+	linker_def on __ehdr_start.
+
 2015-02-14  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/17973
diff --git a/ld/emultempl/elf32.em b/ld/emultempl/elf32.em
index 618e20a..0f22570 100644
--- a/ld/emultempl/elf32.em
+++ b/ld/emultempl/elf32.em
@@ -1570,6 +1570,7 @@ ${ELF_INTERPRETER_SET_DEFAULT}
 	 as it was.  */
       ehdr_start->root.type = ehdr_start_save.type;
       ehdr_start->root.u = ehdr_start_save.u;
+      ehdr_start->root.linker_def = 1;
     }
 }
 
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index 64f0871..b8aeb0a 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-02-18  Alan Modra  <amodra@gmail.com>
+
+	* ld-aarch64/gc-tls-relocs.d,
+	* ld-powerpc/tlsexe.r, * ld-powerpc/tlsexetoc.r,
+	* ld-powerpc/tlsso.r, * ld-powerpc/tlstocso.r: Update.
+
 2015-02-17  Alan Modra  <amodra@gmail.com>
 
 	PR ld/17975
diff --git a/ld/testsuite/ld-aarch64/gc-tls-relocs.d b/ld/testsuite/ld-aarch64/gc-tls-relocs.d
index 191647c..480d869 100644
--- a/ld/testsuite/ld-aarch64/gc-tls-relocs.d
+++ b/ld/testsuite/ld-aarch64/gc-tls-relocs.d
@@ -17,7 +17,6 @@ SYMBOL TABLE:
 0+9000 l    d  \.got	0+ \.got
 0+0000 l    df \*ABS\*	0+ .*
 0+0000 l    df \*ABS\*	0+ 
-0+0000 l       \*UND\*	0+ __tls_get_addr
 0+9000 l     O \.got	0+ _GLOBAL_OFFSET_TABLE_
 0+8000 g       \.text	0+ _start
 
diff --git a/ld/testsuite/ld-powerpc/tlsexe.r b/ld/testsuite/ld-powerpc/tlsexe.r
index 443bae8..94e5272 100644
--- a/ld/testsuite/ld-powerpc/tlsexe.r
+++ b/ld/testsuite/ld-powerpc/tlsexe.r
@@ -98,9 +98,8 @@ Symbol table '\.symtab' contains [0-9]+ entries:
 .* TLS +LOCAL +DEFAULT +8 le5
 .* FILE +LOCAL +DEFAULT +ABS 
 .* OBJECT +LOCAL +DEFAULT +10 _DYNAMIC
-.* (NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve|(FUNC|NOTYPE) +LOCAL +DEFAULT +UND \.__tls_get_addr(|_opt))
-.* (NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt)|NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve)
-.* ((FUNC|NOTYPE) +LOCAL +DEFAULT +UND \.__tls_get_addr(|_opt)|NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt))
+.* NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve
+.* NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt)
 .* GLOBAL +DEFAULT +UND gd
 .* GLOBAL +DEFAULT +9 le0
 .* GLOBAL +DEFAULT +9 ld0
diff --git a/ld/testsuite/ld-powerpc/tlsexetoc.r b/ld/testsuite/ld-powerpc/tlsexetoc.r
index bb6462f..7b55281 100644
--- a/ld/testsuite/ld-powerpc/tlsexetoc.r
+++ b/ld/testsuite/ld-powerpc/tlsexetoc.r
@@ -98,9 +98,8 @@ Symbol table '\.symtab' contains [0-9]+ entries:
 .* NOTYPE +LOCAL +DEFAULT +12 \.Lie0
 .* FILE +LOCAL +DEFAULT +ABS 
 .* OBJECT +LOCAL +DEFAULT +10 _DYNAMIC
-.* (NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve|(FUNC|NOTYPE) +LOCAL +DEFAULT +UND \.__tls_get_addr(|_opt))
-.* (NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt)|NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve)
-.* ((FUNC|NOTYPE) +LOCAL +DEFAULT +UND \.__tls_get_addr(|_opt)|NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt))
+.* NOTYPE +LOCAL +DEFAULT +7 __glink_PLTresolve
+.* NOTYPE +LOCAL +DEFAULT +7 .*\.plt_call\.__tls_get_addr(|_opt)
 .* TLS +GLOBAL +DEFAULT +UND gd
 .* TLS +GLOBAL +DEFAULT +9 le0
 .* TLS +GLOBAL +DEFAULT +9 ld0
diff --git a/ld/testsuite/ld-powerpc/tlsso.r b/ld/testsuite/ld-powerpc/tlsso.r
index 3a5b808..e0a3a75 100644
--- a/ld/testsuite/ld-powerpc/tlsso.r
+++ b/ld/testsuite/ld-powerpc/tlsso.r
@@ -116,7 +116,6 @@ Symbol table '\.symtab' contains [0-9]+ entries:
 .* OBJECT +LOCAL +DEFAULT +9 _DYNAMIC
 .* NOTYPE +LOCAL +DEFAULT +6 .*\.plt_call\.__tls_get_addr
 .* NOTYPE +LOCAL +DEFAULT +6 __glink_PLTresolve
-.* NOTYPE +LOCAL +DEFAULT +UND \.__tls_get_addr
 .* TLS +GLOBAL +DEFAULT +UND gd
 .* TLS +GLOBAL +DEFAULT +8 le0
 .* NOTYPE +GLOBAL +DEFAULT +UND __tls_get_addr
diff --git a/ld/testsuite/ld-powerpc/tlstocso.r b/ld/testsuite/ld-powerpc/tlstocso.r
index 075e303..0006db9 100644
--- a/ld/testsuite/ld-powerpc/tlstocso.r
+++ b/ld/testsuite/ld-powerpc/tlstocso.r
@@ -112,7 +112,6 @@ Symbol table '\.symtab' contains [0-9]+ entries:
 .* OBJECT +LOCAL +DEFAULT +9 _DYNAMIC
 .* NOTYPE +LOCAL +DEFAULT +6 .*\.plt_call\.__tls_get_addr
 .* NOTYPE +LOCAL +DEFAULT +6 __glink_PLTresolve
-.* NOTYPE +LOCAL +DEFAULT +UND \.__tls_get_addr
 .* TLS +GLOBAL +DEFAULT +UND gd
 .* TLS +GLOBAL +DEFAULT +8 le0
 .* NOTYPE +GLOBAL +DEFAULT +UND __tls_get_addr

-- 
Alan Modra
Australia Development Lab, IBM
Follow-Ups:
- Re: Drop undefined local symbols from symtab?
  - From: H.J. Lu
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