Patchwork [Fortran,(RFC)] PR49110/51055 Assignment to alloc. deferred-length character vars

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Submitter Tobias Burnus
Date May 13, 2012, 1:50 p.m.
Message ID <4FAFBC1C.8070902@net-b.de>
Download mbox | patch
Permalink /patch/158836/
State New
Headers show

Comments

Tobias Burnus - May 13, 2012, 1:50 p.m.
Tobias Burnus wrote:
> Note that the patch assumes that the function's result variable's 
> length specification expression is completely known to the caller. I 
> think that's always the case in gfortran - or is it not?

Thinking about it, I came to the conclusion has explicitly been designed 
such that it is known.

Note: The attached patch is required in addition to make sure that the 
variable has the correct name mangling and to ensure that the string 
length is TREE_PUBLIC() = 1, when needed.

The trans-expr.c part of the patch has been posted at 
http://gcc.gnu.org/ml/fortran/2012-05/msg00054.html


Compile ("-c") the following code - with the function commented or not 
and with PUBLIC and PRIVATE - and look resulting .o file via nm. It 
shouldn't show the "str" variable (and the length variable) if (and 
only) if it is private and not used in the function result expression. 
Result for the program as shown below:

0000000000000008 B .__m_MOD_str
0000000000000000 T __m_MOD_bar
0000000000000000 B __m_MOD_str


module m
!  character(len=:), PRIVATE, allocatable :: str
   character(len=:), PUBLIC, allocatable :: str
contains
   ! Note due to technical reasons (TBP, generic, cf. resolve.c),
   ! a "PRIVATE :: bar" still counts a publicly using "str".
   function bar()
     character(len=len(str)) :: str
   end function bar
end module m

Tobias
Paul Richard Thomas - May 14, 2012, 1:31 p.m.
Dear Tobias,

OK for trunk - just a wee typo to correct:
s/+     parameter available to the caller; gfortran save it in the
.mod files. */
/+     parameter available to the caller; gfortran saves it in the
.mod files. *//

Thanks for the patch.

Paul

On 13 May 2012 15:50, Tobias Burnus <burnus@net-b.de> wrote:
> Tobias Burnus wrote:
>>
>> Note that the patch assumes that the function's result variable's length
>> specification expression is completely known to the caller. I think that's
>> always the case in gfortran - or is it not?
>
>
> Thinking about it, I came to the conclusion has explicitly been designed
> such that it is known.
>
> Note: The attached patch is required in addition to make sure that the
> variable has the correct name mangling and to ensure that the string length
> is TREE_PUBLIC() = 1, when needed.
>
> The trans-expr.c part of the patch has been posted at
> http://gcc.gnu.org/ml/fortran/2012-05/msg00054.html
>
>
> Compile ("-c") the following code - with the function commented or not and
> with PUBLIC and PRIVATE - and look resulting .o file via nm. It shouldn't
> show the "str" variable (and the length variable) if (and only) if it is
> private and not used in the function result expression. Result for the
> program as shown below:
>
> 0000000000000008 B .__m_MOD_str
> 0000000000000000 T __m_MOD_bar
> 0000000000000000 B __m_MOD_str
>
>
> module m
> !  character(len=:), PRIVATE, allocatable :: str
>  character(len=:), PUBLIC, allocatable :: str
> contains
>  ! Note due to technical reasons (TBP, generic, cf. resolve.c),
>  ! a "PRIVATE :: bar" still counts a publicly using "str".
>  function bar()
>    character(len=len(str)) :: str
>  end function bar
> end module m
>
> Tobias

Patch

diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index b03d393..3c1118e 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -1087,11 +1087,14 @@  gfc_create_string_length (gfc_symbol * sym)
   if (sym->ts.u.cl->backend_decl == NULL_TREE)
     {
       tree length;
-      char name[GFC_MAX_MANGLED_SYMBOL_LEN + 2];
+      const char *name;
 
       /* Also prefix the mangled name.  */
-      strcpy (&name[1], sym->name);
-      name[0] = '.';
+      if (sym->module)
+	name = gfc_get_string (".__%s_MOD_%s", sym->module, sym->name);
+      else
+	name = gfc_get_string (".%s", sym->name);
+
       length = build_decl (input_location,
 			   VAR_DECL, get_identifier (name),
 			   gfc_charlen_type_node);
@@ -1101,6 +1104,13 @@  gfc_create_string_length (gfc_symbol * sym)
 	gfc_defer_symbol_init (sym);
 
       sym->ts.u.cl->backend_decl = length;
+
+      if (sym->attr.save || sym->ns->proc_name->attr.flavor == FL_MODULE)
+	TREE_STATIC (length) = 1;
+
+      if (sym->ns->proc_name->attr.flavor == FL_MODULE
+	  && (sym->attr.access != ACCESS_PRIVATE || sym->attr.public_used))
+	TREE_PUBLIC (length) = 1;
     }
 
   gcc_assert (sym->ts.u.cl->backend_decl != NULL_TREE);
@@ -1395,29 +1405,7 @@  gfc_get_symbol_decl (gfc_symbol * sym)
 
   gfc_finish_var_decl (decl, sym);
 
-  if (sym->ts.type == BT_CHARACTER)
-    {
-      /* Character variables need special handling.  */
-      gfc_allocate_lang_decl (decl);
-
-      if (TREE_CODE (length) != INTEGER_CST)
-	{
-	  char name[GFC_MAX_MANGLED_SYMBOL_LEN + 2];
-
-	  if (sym->module)
-	    {
-	      /* Also prefix the mangled name for symbols from modules.  */
-	      strcpy (&name[1], sym->name);
-	      name[0] = '.';
-	      strcpy (&name[1],
-		      IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (length)));
-	      gfc_set_decl_assembler_name (decl, get_identifier (name));
-	    }
-	  gfc_finish_var_decl (length, sym);
-	  gcc_assert (!sym->value);
-	}
-    }
-  else if (sym->attr.subref_array_pointer)
+  if (sym->attr.subref_array_pointer)
     {
       /* We need the span for these beasts.  */
       gfc_allocate_lang_decl (decl);