Re: gas rearranging elf file symbols

Re: gas rearranging elf file symbols

[Jan Beulich]

This doesn't look correct to me. What I believe needs to be cut down is
the number of symbols resulting from (from the assembler's perspective)
consecutive # <line> <file> preprocessor-generated constructs (because
all of them except the last can only be meaningless except for
dependency determination). Explicit .file/.appfile directives should, in
my opinion, always be honoured. If you really want just a single file
symbol, then I'd still see a need to honor the first (or last)
.file/.appfile in preference over any preprocessor-generated ones. Jan

>>> Alan Modra <amodra@bigpond.net.au> 20.10.04 04:29:03 >>>
On Fri, Oct 08, 2004 at 03:59:29PM +0930, Alan Modra wrote:
> STT_FILE
>     Conventionally, the symbol's name gives the name of the source
file
>     associated with the object file. A file symbol has STB_LOCAL
>     binding, its section index is SHN_ABS, and it precedes the other
>     STB_LOCAL symbols for the file, if it is present.
> 
> From that wording you could also infer that there should only be one
> file symbol, that of the main source file.

I'm inclined to implement this.  gcc/gas seem to only emit one file
symbol for C source, so I think it reasonable to do the same for
assembly.  The difference in number of symbols can be quite
significant,
for example glibc/io/write.o on powerpc-linux currently has 38 file
symbols (in a total of 49 symbols).

	* config/obj-elf.c (elf_file_symbol): Only emit one file
symbol.

Any objections from gdb folks?

Index: gas/config/obj-elf.c
===================================================================
RCS file: /cvs/src/src/gas/config/obj-elf.c,v
retrieving revision 1.86
diff -u -p -r1.86 obj-elf.c
--- gas/config/obj-elf.c	8 Sep 2004 20:52:48 -0000	1.86
+++ gas/config/obj-elf.c	20 Oct 2004 02:23:13 -0000
@@ -238,19 +238,24 @@ elf_sec_sym_ok_for_reloc (asection *sec)
 void
 elf_file_symbol (const char *s)
 {
-  symbolS *sym;
+  if (symbol_rootP == NULL
+      || symbol_rootP->bsym == NULL
+      || (symbol_rootP->bsym->flags & BSF_FILE) == 0)
+    {
+      symbolS *sym;
 
-  sym = symbol_new (s, absolute_section, 0, NULL);
-  symbol_set_frag (sym, &zero_address_frag);
-  symbol_get_bfdsym (sym)->flags |= BSF_FILE;
+      sym = symbol_new (s, absolute_section, 0, NULL);
+      symbol_set_frag (sym, &zero_address_frag);
+      symbol_get_bfdsym (sym)->flags |= BSF_FILE;
 
-  if (symbol_rootP != sym)
-    {
-      symbol_remove (sym, &symbol_rootP, &symbol_lastP);
-      symbol_insert (sym, symbol_rootP, &symbol_rootP,
&symbol_lastP);
+      if (symbol_rootP != sym)
+	{
+	  symbol_remove (sym, &symbol_rootP, &symbol_lastP);
+	  symbol_insert (sym, symbol_rootP, &symbol_rootP,
&symbol_lastP);
 #ifdef DEBUG
-      verify_symbol_chain (symbol_rootP, symbol_lastP);
+	  verify_symbol_chain (symbol_rootP, symbol_lastP);
 #endif
+	}
     }
 
 #ifdef NEED_ECOFF_DEBUG

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Re: gas rearranging elf file symbols

[Alan Modra]

On Wed, Oct 20, 2004 at 08:42:12AM +0200, Jan Beulich wrote:
> Explicit .file/.appfile directives should, in
> my opinion, always be honoured.

Yes, you are right.  I should modify the patch so that I only discard
multiple file symbols generated by # preprocessor lines.

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Re: gas rearranging elf file symbols

[Alan Modra]

On Thu, Oct 21, 2004 at 09:18:39AM +0930, Alan Modra wrote:
> On Wed, Oct 20, 2004 at 08:42:12AM +0200, Jan Beulich wrote:
> > Explicit .file/.appfile directives should, in
> > my opinion, always be honoured.
> 
> Yes, you are right.  I should modify the patch so that I only discard
> multiple file symbols generated by # preprocessor lines.

Since I heard no complaints from the gdb folk about this idea, I'm
applying the following.

gas/ChangeLog
	* obj.h (struct format_ops <app_file>): Add int param.
	* read.h (s_app_file_string): Likewise.
	* read.c (s_app_file_string): Likewise.
	(s_app_file): Adjust s_app_file_string call.
	* config/tc-mips.c (s_mips_file): Likewise.
	* config/obj-coff.h (obj_app_file): Add app param.
	* config/obj-ecoff.h (obj_app_file): Likewise.
	* config/obj-multi.h (obj_app_file): Likewise.
	* config/obj-elf.h (elf_file_symbol): Likewise.
	* config/obj-elf.c (elf_file_symbol): Only emit one file symbol
	if called for # preprocessor lines.

Index: gas/obj.h
===================================================================
RCS file: /cvs/src/src/gas/obj.h,v
retrieving revision 1.7
diff -u -p -r1.7 obj.h
--- gas/obj.h	3 Dec 2003 03:39:58 -0000	1.7
+++ gas/obj.h	10 Nov 2004 02:40:28 -0000
@@ -51,7 +51,7 @@ struct format_ops {
   unsigned dfl_leading_underscore : 1;
   unsigned emit_section_symbols : 1;
   void (*begin) (void);
-  void (*app_file) (const char *);
+  void (*app_file) (const char *, int);
   void (*frob_symbol) (symbolS *, int *);
   void (*frob_file) (void);
   void (*frob_file_before_adjust) (void);
Index: gas/read.c
===================================================================
RCS file: /cvs/src/src/gas/read.c,v
retrieving revision 1.79
diff -u -p -r1.79 read.c
--- gas/read.c	13 Aug 2004 19:53:51 -0000	1.79
+++ gas/read.c	10 Nov 2004 02:40:30 -0000
@@ -1570,7 +1570,7 @@ s_data (int ignore ATTRIBUTE_UNUSED)
    .file.  */
 
 void
-s_app_file_string (char *file)
+s_app_file_string (char *file, int appfile)
 {
 #ifdef LISTING
   if (listing)
@@ -1578,7 +1578,7 @@ s_app_file_string (char *file)
 #endif
   register_dependency (file);
 #ifdef obj_app_file
-  obj_app_file (file);
+  obj_app_file (file, appfile);
 #endif
 }
 
@@ -1606,7 +1606,7 @@ s_app_file (int appfile)
 
       demand_empty_rest_of_line ();
       if (!may_omit)
-	s_app_file_string (s);
+	s_app_file_string (s, appfile);
     }
 }
 
Index: gas/read.h
===================================================================
RCS file: /cvs/src/src/gas/read.h,v
retrieving revision 1.23
diff -u -p -r1.23 read.h
--- gas/read.h	9 Feb 2004 12:12:42 -0000	1.23
+++ gas/read.h	10 Nov 2004 02:40:30 -0000
@@ -139,7 +139,7 @@ extern void bss_alloc (symbolS *, addres
 extern offsetT parse_align (int);
 extern symbolS *s_comm_internal (int, symbolS *(*) (int, symbolS *, addressT));
 extern symbolS *s_lcomm_internal (int, symbolS *, addressT);
-extern void s_app_file_string (char *);
+extern void s_app_file_string (char *, int);
 extern void s_app_file (int);
 extern void s_app_line (int);
 extern void s_bad_endr (int);
Index: gas/config/obj-coff.h
===================================================================
RCS file: /cvs/src/src/gas/config/obj-coff.h,v
retrieving revision 1.22
diff -u -p -r1.22 obj-coff.h
--- gas/config/obj-coff.h	8 Nov 2004 13:17:22 -0000	1.22
+++ gas/config/obj-coff.h	10 Nov 2004 02:40:31 -0000
@@ -397,7 +397,7 @@ extern int coff_n_line_nos;
 extern void coff_add_linesym PARAMS ((symbolS *));
 
 void c_dot_file_symbol PARAMS ((const char *filename));
-#define obj_app_file c_dot_file_symbol
+#define obj_app_file(name, app) c_dot_file_symbol (name)
 
 extern void coff_frob_symbol PARAMS ((symbolS *, int *));
 extern void coff_adjust_symtab PARAMS ((void));
@@ -840,7 +840,7 @@ extern segT obj_coff_add_segment PARAMS 
 extern void obj_coff_section PARAMS ((int));
 
 extern void c_dot_file_symbol PARAMS ((char *filename));
-#define obj_app_file c_dot_file_symbol
+#define obj_app_file(name, app) c_dot_file_symbol (name)
 extern void obj_extra_stuff PARAMS ((object_headers * headers));
 
 extern segT s_get_segment PARAMS ((symbolS *ptr));
Index: gas/config/obj-ecoff.h
===================================================================
RCS file: /cvs/src/src/gas/config/obj-ecoff.h,v
retrieving revision 1.4
diff -u -p -r1.4 obj-ecoff.h
--- gas/config/obj-ecoff.h	5 Sep 2002 00:01:16 -0000	1.4
+++ gas/config/obj-ecoff.h	10 Nov 2004 02:40:31 -0000
@@ -63,7 +63,7 @@ extern void ecoff_frob_file PARAMS ((voi
 #define obj_symbol_new_hook ecoff_symbol_new_hook
 
 /* Record file switches in the ECOFF symbol table.  */
-#define obj_app_file(name) ecoff_new_file (name)
+#define obj_app_file(name, app) ecoff_new_file (name)
 
 /* At the moment we don't want to do any stabs processing in read.c.  */
 #define OBJ_PROCESS_STAB(seg, what, string, type, other, desc) \
Index: gas/config/obj-elf.c
===================================================================
RCS file: /cvs/src/src/gas/config/obj-elf.c,v
retrieving revision 1.86
diff -u -p -r1.86 obj-elf.c
--- gas/config/obj-elf.c	8 Sep 2004 20:52:48 -0000	1.86
+++ gas/config/obj-elf.c	10 Nov 2004 02:40:32 -0000
@@ -236,21 +236,27 @@ elf_sec_sym_ok_for_reloc (asection *sec)
 }
 
 void
-elf_file_symbol (const char *s)
+elf_file_symbol (const char *s, int appfile)
 {
-  symbolS *sym;
+  if (!appfile
+      || symbol_rootP == NULL
+      || symbol_rootP->bsym == NULL
+      || (symbol_rootP->bsym->flags & BSF_FILE) == 0)
+    {
+      symbolS *sym;
 
-  sym = symbol_new (s, absolute_section, 0, NULL);
-  symbol_set_frag (sym, &zero_address_frag);
-  symbol_get_bfdsym (sym)->flags |= BSF_FILE;
+      sym = symbol_new (s, absolute_section, 0, NULL);
+      symbol_set_frag (sym, &zero_address_frag);
+      symbol_get_bfdsym (sym)->flags |= BSF_FILE;
 
-  if (symbol_rootP != sym)
-    {
-      symbol_remove (sym, &symbol_rootP, &symbol_lastP);
-      symbol_insert (sym, symbol_rootP, &symbol_rootP, &symbol_lastP);
+      if (symbol_rootP != sym)
+	{
+	  symbol_remove (sym, &symbol_rootP, &symbol_lastP);
+	  symbol_insert (sym, symbol_rootP, &symbol_rootP, &symbol_lastP);
 #ifdef DEBUG
-      verify_symbol_chain (symbol_rootP, symbol_lastP);
+	  verify_symbol_chain (symbol_rootP, symbol_lastP);
 #endif
+	}
     }
 
 #ifdef NEED_ECOFF_DEBUG
Index: gas/config/obj-elf.h
===================================================================
RCS file: /cvs/src/src/gas/config/obj-elf.h,v
retrieving revision 1.22
diff -u -p -r1.22 obj-elf.h
--- gas/config/obj-elf.h	13 Dec 2003 12:57:40 -0000	1.22
+++ gas/config/obj-elf.h	10 Nov 2004 02:40:32 -0000
@@ -159,7 +159,7 @@ extern void elf_frob_file_after_relocs (
 #ifndef obj_app_file
 #define obj_app_file elf_file_symbol
 #endif
-extern void elf_file_symbol (const char *);
+extern void elf_file_symbol (const char *, int);
 
 extern void obj_elf_section_change_hook (void);
 
Index: gas/config/obj-multi.h
===================================================================
RCS file: /cvs/src/src/gas/config/obj-multi.h,v
retrieving revision 1.8
diff -u -p -r1.8 obj-multi.h
--- gas/config/obj-multi.h	5 Sep 2002 00:01:16 -0000	1.8
+++ gas/config/obj-multi.h	10 Nov 2004 02:40:32 -0000
@@ -37,9 +37,9 @@
 	 ? (*this_format->begin) ()			\
 	 : (void) 0)
 
-#define obj_app_file(NAME)				\
+#define obj_app_file(NAME, APPFILE)			\
 	(this_format->app_file				\
-	 ? (*this_format->app_file) (NAME)		\
+	 ? (*this_format->app_file) (NAME, APPFILE)	\
 	 : (void) 0)
 
 #define obj_frob_symbol(S,P)				\
Index: gas/config/tc-mips.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-mips.c,v
retrieving revision 1.273
diff -u -p -r1.273 tc-mips.c
--- gas/config/tc-mips.c	7 Oct 2004 22:29:18 -0000	1.273
+++ gas/config/tc-mips.c	10 Nov 2004 02:40:39 -0000
@@ -13508,7 +13508,7 @@ s_mips_file (int x ATTRIBUTE_UNUSED)
       if (filename != NULL && ! first_file_directive)
 	{
 	  (void) new_logical_line (filename, -1);
-	  s_app_file_string (filename);
+	  s_app_file_string (filename, 0);
 	}
       first_file_directive = 1;
     }

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Re: gas rearranging elf file symbols

[Alan Modra]

On Fri, Oct 08, 2004 at 03:59:29PM +0930, Alan Modra wrote:
> STT_FILE
>     Conventionally, the symbol's name gives the name of the source file
>     associated with the object file. A file symbol has STB_LOCAL
>     binding, its section index is SHN_ABS, and it precedes the other
>     STB_LOCAL symbols for the file, if it is present.
> 
> From that wording you could also infer that there should only be one
> file symbol, that of the main source file.

I'm inclined to implement this.  gcc/gas seem to only emit one file
symbol for C source, so I think it reasonable to do the same for
assembly.  The difference in number of symbols can be quite significant,
for example glibc/io/write.o on powerpc-linux currently has 38 file
symbols (in a total of 49 symbols).

	* config/obj-elf.c (elf_file_symbol): Only emit one file symbol.

Any objections from gdb folks?

Index: gas/config/obj-elf.c
===================================================================
RCS file: /cvs/src/src/gas/config/obj-elf.c,v
retrieving revision 1.86
diff -u -p -r1.86 obj-elf.c
--- gas/config/obj-elf.c	8 Sep 2004 20:52:48 -0000	1.86
+++ gas/config/obj-elf.c	20 Oct 2004 02:23:13 -0000
@@ -238,19 +238,24 @@ elf_sec_sym_ok_for_reloc (asection *sec)
 void
 elf_file_symbol (const char *s)
 {
-  symbolS *sym;
+  if (symbol_rootP == NULL
+      || symbol_rootP->bsym == NULL
+      || (symbol_rootP->bsym->flags & BSF_FILE) == 0)
+    {
+      symbolS *sym;
 
-  sym = symbol_new (s, absolute_section, 0, NULL);
-  symbol_set_frag (sym, &zero_address_frag);
-  symbol_get_bfdsym (sym)->flags |= BSF_FILE;
+      sym = symbol_new (s, absolute_section, 0, NULL);
+      symbol_set_frag (sym, &zero_address_frag);
+      symbol_get_bfdsym (sym)->flags |= BSF_FILE;
 
-  if (symbol_rootP != sym)
-    {
-      symbol_remove (sym, &symbol_rootP, &symbol_lastP);
-      symbol_insert (sym, symbol_rootP, &symbol_rootP, &symbol_lastP);
+      if (symbol_rootP != sym)
+	{
+	  symbol_remove (sym, &symbol_rootP, &symbol_lastP);
+	  symbol_insert (sym, symbol_rootP, &symbol_rootP, &symbol_lastP);
 #ifdef DEBUG
-      verify_symbol_chain (symbol_rootP, symbol_lastP);
+	  verify_symbol_chain (symbol_rootP, symbol_lastP);
 #endif
+	}
     }
 
 #ifdef NEED_ECOFF_DEBUG

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre