From John Reiser <jreiser@BitWagon.com>

* ldlang.c (lang_common): Conditionally inhibit Common allocation.
	* lexsup.c: Add --no-define-common commandline option.
	* ldgram.y: Add INHIBIT_COMMON_ALLOCATION script command.
	* ldlex.l: Likewise.
	* ld.h: Add command_line.inhibit_common_definition.
	* ldmain.c (main): Initialize.
	* ld.texinfo: Document.

ld/ChangeLog

@@ -1,6 +1,12 @@
-2001-09-29  Alan Modra  <amodra@bigpond.net.au>
+2001-09-29  John Reiser  <jreiser@BitWagon.com>
 
-	* ldlang.c (section_already_linked): Remove assignment to kept_section.
+	* ldlang.c (lang_common): Conditionally inhibit Common allocation.
+	* lexsup.c: Add --no-define-common commandline option.
+	* ldgram.y: Add INHIBIT_COMMON_ALLOCATION script command.
+	* ldlex.l: Likewise.
+	* ld.h: Add command_line.inhibit_common_definition.
+	* ldmain.c (main): Initialize.
+	* ld.texinfo: Document.
 
 2001-09-26  Alan Modra  <amodra@bigpond.net.au>
 

ld/ld.h

@@ -102,6 +102,9 @@ typedef struct user_section_struct {
 typedef struct {
   /* 1 => assign space to common symbols even if `relocatable_output'.  */
   boolean force_common_definition;
+
+  /* 1 => do not assign addresses to common symbols. */
+  boolean inhibit_common_definition;
   boolean relax;
 
   /* Name of runtime interpreter to invoke.  */

ld/ld.texinfo

@@ -950,6 +950,24 @@ sorted by name.  For each symbol, a list of file names is given.  If the
 symbol is defined, the first file listed is the location of the
 definition.  The remaining files contain references to the symbol.
 
+@cindex common allocation
+@kindex --no-define-common
+@item --no-define-common
+This option inhibits the assignment of addresses to common symbols.
+The script command @code{INHIBIT_COMMON_ALLOCATION} has the same effect.
+@xref{Miscellaneous Commands}.
+
+The @samp{--no-define-common} option allows decoupling
+the decision to assign addresses to Common symbols from the choice
+of the output file type; otherwise a non-Relocatable output type
+forces assigning addresses to Common symbols.
+Using @samp{--no-define-common} allows Common symbols that are referenced
+from a shared library to be assigned addresses only in the main program.
+This eliminates the unused duplicate space in the shared library,
+and also prevents any possible confusion over resolving to the wrong
+duplicate when there are many dynamic modules with specialized search
+paths for runtime symbol resolution.
+
 @cindex symbols, from command line
 @kindex --defsym @var{symbol}=@var{exp}
 @item --defsym @var{symbol}=@var{expression}
@@ -2311,6 +2329,13 @@ This command has the same effect as the @samp{-d} command-line option:
 to make @code{ld} assign space to common symbols even if a relocatable
 output file is specified (@samp{-r}).
 
+@item INHIBIT_COMMON_ALLOCATION
+@kindex INHIBIT_COMMON_ALLOCATION
+@cindex common allocation in linker script
+This command has the same effect as the @samp{--no-define-common}
+command-line option: to make @code{ld} omit the assignment of addresses
+to common symbols even for a non-relocatable output file.
+
 @item NOCROSSREFS(@var{section} @var{section} @dots{})
 @kindex NOCROSSREFS(@var{sections})
 @cindex cross references

ld/ldgram.y

@@ -125,6 +125,7 @@ static int error_index;
 %token SECTIONS PHDRS SORT
 %token '{' '}'
 %token SIZEOF_HEADERS OUTPUT_FORMAT FORCE_COMMON_ALLOCATION OUTPUT_ARCH
+%token INHIBIT_COMMON_ALLOCATION
 %token SIZEOF_HEADERS
 %token INCLUDE
 %token MEMORY DEFSYMEND
@@ -321,6 +322,8 @@ ifile_p1:
 		  { ldfile_set_output_arch($3); }
 	|	FORCE_COMMON_ALLOCATION
 		{ command_line.force_common_definition = true ; }
+	|	INHIBIT_COMMON_ALLOCATION
+		{ command_line.inhibit_common_definition = true ; }
 	|	INPUT '(' input_list ')'
 	|	GROUP
 		  { lang_enter_group (); }

ld/ldlang.c

@@ -3550,6 +3550,8 @@ lang_check ()
 static void
 lang_common ()
 {
+  if (command_line.inhibit_common_definition)
+    return;
   if (link_info.relocateable
       && ! command_line.force_common_definition)
     return;

ld/ldlex.l

@@ -260,6 +260,7 @@ V_IDENTIFIER [*?.$_a-zA-Z]([*?.$_a-zA-Z0-9]|::)*
 <BOTH,SCRIPT>"CREATE_OBJECT_SYMBOLS"	{ RTOKEN(CREATE_OBJECT_SYMBOLS);}
 <BOTH,SCRIPT>"CONSTRUCTORS"		{ RTOKEN( CONSTRUCTORS);}
 <BOTH,SCRIPT>"FORCE_COMMON_ALLOCATION" { RTOKEN(FORCE_COMMON_ALLOCATION);}
+<BOTH,SCRIPT>"INHIBIT_COMMON_ALLOCATION" { RTOKEN(INHIBIT_COMMON_ALLOCATION);}
 <BOTH,SCRIPT>"SECTIONS"		{ RTOKEN(SECTIONS);}
 <BOTH,SCRIPT>"FILL"			{ RTOKEN(FILL);}
 <BOTH,SCRIPT>"STARTUP"		{ RTOKEN(STARTUP);}

ld/ldmain.c

@@ -205,6 +205,7 @@ main (argc, argv)
   config.split_by_reloc = (unsigned) -1;
   config.split_by_file = (bfd_size_type) -1;
   command_line.force_common_definition = false;
+  command_line.inhibit_common_definition = false;
   command_line.interpreter = NULL;
   command_line.rpath = NULL;
   command_line.warn_mismatch = true;

ld/lexsup.c

@@ -132,6 +132,7 @@ int parsing_defsym = 0;
 #define OPTION_ALLOW_SHLIB_UNDEFINED	(OPTION_TARGET_HELP + 1)
 #define OPTION_DISCARD_NONE		(OPTION_ALLOW_SHLIB_UNDEFINED + 1)
 #define OPTION_SPARE_DYNAMIC_TAGS	(OPTION_DISCARD_NONE + 1)
+#define OPTION_NO_DEFINE_COMMON		(OPTION_SPARE_DYNAMIC_TAGS + 1)
 
 /* The long options.  This structure is used for both the option
    parsing and the help text.  */
@@ -311,6 +312,8 @@ static const struct ld_option ld_options[] =
      '\0', N_("SYMBOL"), N_("Call SYMBOL at load-time"), ONE_DASH },
   { {"Map", required_argument, NULL, OPTION_MAP},
       '\0', N_("FILE"), N_("Write a map file"), ONE_DASH },
+  { {"no-define-common", no_argument, NULL, OPTION_NO_DEFINE_COMMON},
+      '\0', NULL, N_("Do not define Common storage"), TWO_DASHES },
   { {"no-demangle", no_argument, NULL, OPTION_NO_DEMANGLE },
       '\0', NULL, N_("Do not demangle symbol names"), TWO_DASHES },
   { {"no-keep-memory", no_argument, NULL, OPTION_NO_KEEP_MEMORY},
@@ -747,6 +750,9 @@ parse_args (argc, argv)
 	  config.magic_demand_paged = false;
 	  config.dynamic_link = false;
 	  break;
+	case OPTION_NO_DEFINE_COMMON:
+	  command_line.inhibit_common_definition = true;
+	  break;
 	case OPTION_NO_DEMANGLE:
 	  demangling = false;
 	  break;