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[RFC PATCH 4/4] Convert NT weak externals to locals


This patch allows converting a weak external symbol to a local symbol
by setting up its section and value to the ones of the alternate
symbol. This is useful when we want to make only a few selected
symbols visible (e.g. objcopy -G).

bfd/

2015-10-22  Octavian Purdila <octavian.purdila@intel.com>

    * coffgen.c: add coff_nt_weak_to_local() that implements weak
      external to local symbol conversion
    * coffcode.h (coff_write_object_contents): call
      coff_nt_weak_to_local()
    * libcoff.h: add coff_nt_weak_to_local() declaration

binutils/

2015-10-22  Octavian Purdila <octavian.purdila@intel.com>

    * objcopy.c (filter_symbols): allow converting undefined weak
      symbols to local symbols for PE since all PE weak symbols are
      undefined

The conversion is triggered when an NT weak external symbol has been
marked with BSF_LOCAL.
---
 bfd/ChangeLog      |  8 ++++++++
 bfd/coffcode.h     |  1 +
 bfd/coffgen.c      | 43 +++++++++++++++++++++++++++++++++++++++++++
 bfd/libcoff.h      |  2 ++
 binutils/ChangeLog |  6 ++++++
 binutils/objcopy.c |  5 ++++-
 6 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index c91c5cb..bb97a9c 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,13 @@
 2015-10-22  Octavian Purdila <octavian.purdila@intel.com>
 
+	* coffgen.c: add coff_nt_weak_to_local() that implements weak
+	external to local symbol conversion
+	* coffcode.h (coff_write_object_contents): call
+	coff_nt_weak_to_local()
+	* libcoff.h: add coff_nt_weak_to_local() declaration
+
+2015-10-22  Octavian Purdila <octavian.purdila@intel.com>
+
 	* cofflink.c (_bfd_coff_link_input_bfd): relocate AUX entries for
 	weak externals when generating relocatable objects
 
diff --git a/bfd/coffcode.h b/bfd/coffcode.h
index 2499885..fc61dee 100644
--- a/bfd/coffcode.h
+++ b/bfd/coffcode.h
@@ -4202,6 +4202,7 @@ coff_write_object_contents (bfd * abfd)
     {
       int firstundef;
 
+      coff_nt_weak_to_local(abfd);
       if (!coff_renumber_symbols (abfd, &firstundef))
 	return FALSE;
       coff_mangle_symbols (abfd);
diff --git a/bfd/coffgen.c b/bfd/coffgen.c
index 9257f73..dd05823 100644
--- a/bfd/coffgen.c
+++ b/bfd/coffgen.c
@@ -788,6 +788,49 @@ coff_renumber_symbols (bfd *bfd_ptr, int *first_undef)
   return TRUE;
 }
 
+/* Transform weak externals to local symbols if requested (e.g. objcopy). */
+void coff_nt_weak_to_local(bfd *abfd)
+{
+  unsigned int symbol_count = bfd_get_symcount (abfd);
+  asymbol **symbol_ptr_ptr = abfd->outsymbols;
+  unsigned int symbol_index;
+
+  for (symbol_index = 0; symbol_index < symbol_count; symbol_index++)
+    {
+      asymbol *symbol = symbol_ptr_ptr[symbol_index];
+      coff_symbol_type *coff_symbol_ptr;
+      combined_entry_type *native;
+      struct internal_syment *sym;
+
+      coff_symbol_ptr = coff_symbol_from (symbol);
+      if (!coff_symbol_ptr)
+        continue;
+
+      native = coff_symbol_ptr->native;
+      if (!native)
+        continue;
+
+      sym = &native->u.syment;
+
+      if ((symbol->flags & BSF_LOCAL) && sym->n_sclass == C_NT_WEAK
+	  && sym->n_numaux == 1) {
+        union internal_auxent *aux = &native[1].u.auxent;
+	struct internal_syment *wsym = &aux->x_sym.x_tagndx.p->u.syment;
+
+	if (!wsym) {
+	  symbol->flags &= BSF_LOCAL;
+	  continue;
+	}
+
+	symbol->flags &= ~BSF_WEAK;
+	symbol->value = wsym->n_value;
+	symbol->section = coff_section_from_bfd_index (abfd, wsym->n_scnum);
+	symbol->section->output_section = symbol->section;
+	sym->n_numaux = 0;
+      }
+    }
+}
+
 /* Run thorough the symbol table again, and fix it so that all
    pointers to entries are changed to the entries' index in the output
    symbol table.  */
diff --git a/bfd/libcoff.h b/bfd/libcoff.h
index 124e603..3ccf4d6 100644
--- a/bfd/libcoff.h
+++ b/bfd/libcoff.h
@@ -309,6 +309,8 @@ extern long coff_canonicalize_symtab
   (bfd *, asymbol **);
 extern int coff_count_linenumbers
   (bfd *);
+extern void coff_nt_weak_to_local
+  (bfd *);
 extern bfd_boolean coff_renumber_symbols
   (bfd *, int *);
 extern void coff_mangle_symbols
diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 16ed7c4..670800e 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,9 @@
+2015-10-22  Octavian Purdila <octavian.purdila@intel.com>
+
+	* objcopy.c (filter_symbols): allow converting undefined weak
+	symbols to local symbols for PE since all PE weak symbols are
+	undefined
+
 2015-09-29  Andrew Stubbs  <ams@codesourcery.com>
 	    H.J. Lu  <hongjiu.lu@intel.com>
 
diff --git a/binutils/objcopy.c b/binutils/objcopy.c
index 2cd55fd..94b7702 100644
--- a/binutils/objcopy.c
+++ b/binutils/objcopy.c
@@ -1372,7 +1372,10 @@ filter_symbols (bfd *abfd, bfd *obfd, asymbol **osyms,
 	      sym->flags |= BSF_WEAK;
 	    }
 
-	  if (!undefined
+	  /* We want to check even undefined weak symbols in the case of PE,
+	   * since weak externals are classified as undefined. */
+	  if ((!undefined || (bfd_get_flavour (abfd) == bfd_target_coff_flavour &&
+			      CONST_STRNEQ ((abfd)->xvec->name, "pe")))
 	      && (flags & (BSF_GLOBAL | BSF_WEAK))
 	      && (is_specified_symbol (name, localize_specific_htab)
 		  || (htab_elements (keepglobal_specific_htab) != 0
-- 
2.1.0


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