(patch) PE-COFF type tags in exported symbols

(patch) PE-COFF type tags in exported symbols

[Mumit Khan]

The following adds support for type tags in exported symbols; Ian added
partial support in dlltool last year, and this is just some finishing
touches. 

This helps tracking down bugs in code that import variables from DLLs. 
The correct way to do import/export is the following:

  /* dll code. */
  __attribute__((dllexport)) int dll_var;

  /* user code. */
  __attribute__((dllimport)) extern int dll_var;
  
If you now forget the dllimport in user code, the code will simply crash
and it's a painful process when porting large packages. MSVC handles this
problem in one of two ways:
  
  - add a "data" type tag in the .drectve section (eg., 
   `-export:dll_var,data' instead of just `-export:dll_var'). This of
   course needs GCC support, and the patch is on its way. The syntax
   is compatible with what native compiler emits.
  - use DATA tag in the export definition file (GNU supports this)

In either case, the import library will not contain "dll_var", but only
__imp__dll_var, so that you'll get link errors instead of runtime crash.

(Note for DJ) I do have changes for pe-dll code as well, but not including
that since the changes are somewhat unclean, mostly due to the difference 
in the way pe-dll handles this issue (uses the same parser). Suggestions 
welcome. 

Sat Aug 28 12:43:04 1999  Mumit Khan  <khan@xraylith.wisc.edu>

	* dlltool.c (scan_drectve_symbols): Handle type tags in exported
	symbols.
	(scan_filtered_symbols): Likewise.
	
Index: dlltool.c
===================================================================
RCS file: /homes/khan/src/CVSROOT/binutils/binutils/dlltool.c,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 dlltool.c
--- dlltool.c	1999/08/14 17:26:25	1.1.1.1
+++ dlltool.c	1999/08/28 06:52:26
@@ -1178,7 +1178,9 @@ scan_drectve_symbols (abfd)
   inform (_("Sucking in info from %s section in %s\n"),
 	  DRECTVE_SECTION_NAME, bfd_get_filename (abfd));
 
-  /* Search for -export: strings */
+  /* Search for -export: strings. The exported symbols can optionally
+     have type tags (eg., -export:foo,data), so handle those as well. 
+     Currently only data tag is supported. */
   p = buf;
   e = buf + size;
   while (p < e)
@@ -1188,25 +1190,36 @@ scan_drectve_symbols (abfd)
 	{
 	  char * name;
 	  char * c;
+	  flagword flags = BSF_FUNCTION;
 	  
 	  p += 8;
 	  name = p;
-	  while (p < e && *p != ' ' && *p != '-')
+	  while (p < e && *p != ',' && *p != ' ' && *p != '-')
 	    p++;
 	  c = xmalloc (p - name + 1);
 	  memcpy (c, name, p - name);
 	  c[p - name] = 0;
+	  if (p < e && *p == ',')	/* found type tag. */
+	    {
+	      char *tag_start = ++p;
+	      while (p < e && *p != ' ' && *p != '-')
+		p++;
+	      if (strncmp (tag_start, "data", 4) == 0)
+	        flags &= ~BSF_FUNCTION;
+	    }
+
 
 	  /* FIXME: The 5th arg is for the `constant' field.
 	     What should it be?  Not that it matters since it's not
 	     currently useful.  */
-	  def_exports (c, 0, -1, 0, 0, 0);
+	  def_exports (c, 0, -1, 0, 0, ! (flags & BSF_FUNCTION));
 
 	  if (add_stdcall_alias && strchr (c, '@'))
 	    {
 	      char *exported_name = xstrdup (c);
 	      char *atsym = strchr (exported_name, '@');
 	      *atsym = '\0';
+	      /* Note: stdcall alias symbols can never be data. */
 	      def_exports (exported_name, xstrdup (c), -1, 0, 0, 0);
 	    }
 	}
@@ -1248,13 +1261,15 @@ scan_filtered_symbols (abfd, minisyms, s
       if (bfd_get_symbol_leading_char (abfd) == symbol_name[0])
 	++symbol_name;
 
-      def_exports (xstrdup (symbol_name) , 0, -1, 0, 0, 0);
+      def_exports (xstrdup (symbol_name) , 0, -1, 0, 0,
+                   ! (sym->flags & BSF_FUNCTION));
 
       if (add_stdcall_alias && strchr (symbol_name, '@'))
         {
 	  char *exported_name = xstrdup (symbol_name);
 	  char *atsym = strchr (exported_name, '@');
 	  *atsym = '\0';
+	  /* Note: stdcall alias symbols can never be data. */
 	  def_exports (exported_name, xstrdup (symbol_name), -1, 0, 0, 0);
 	}
     }

Regards,
Mumit