Bug 62309 - -fno-automatic with -finit-local prevents initialization of automatics in recursive functions
Summary: -fno-automatic with -finit-local prevents initialization of automatics in rec...
Status: RESOLVED FIXED
Alias: None
Product: gcc
Classification: Unclassified
Component: fortran (show other bugs)
Version: 4.8.3
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2014-08-29 20:08 UTC by Fritz Reese
Modified: 2014-08-31 22:31 UTC (History)
1 user (show)

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Target:
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Known to work:
Known to fail:
Last reconfirmed:


Attachments
Patch and testcase (774 bytes, patch)
2014-08-29 20:10 UTC, Fritz Reese
Details | Diff

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Description Fritz Reese 2014-08-29 20:08:26 UTC
It seems with gcc-4.8.3 -fno-automatic prevents initializers from being applied to automatic variables. The following does not behave as I would expect it to with (linux-x86-64):

      function f (x)
        implicit none
        integer f, x
        integer a ! should be SAVEd from -fno-automatic
        a = a + x ! should increment by y every time
        f = a
        return
      endfunction
       
      recursive function g (x)
        implicit none
        integer g, x
        integer b ! should be automatic from recursive
        b = b + x ! should be set to y every time
        g = b
        return
      endfunction

      implicit none
      integer f, g

      ! Should return static value of a; accumulates x
      print *, f(3) ! -> 3, ok
      print *, f(4) ! -> 7, ok
      print *, f(2) ! -> 2, ok

      ! Should return automatic value of c; equal to y each time
      print *, g(3) ! -> garbage, expected 3
      print *, g(4) ! -> garbage, expected 4
      print *, g(2) ! -> garbage, expected 2

      end
$ gfortran -fno-automatic -finit-local-zero auto_test.f
$ ./a.out
           3
           7
           9
       32770
       32771
       32769
$

According to gfortran's manual page, -fno-automatic should "Treat each program unit (except those marked as RECURSIVE) as if the "SAVE" statement were specified for every local variable [...]". As far as I can tell, -finit-local-zero should still initialize automatic variables in RECURSIVE functions.
Comment 1 Fritz Reese 2014-08-29 20:10:33 UTC
Created attachment 33418 [details]
Patch and testcase

I believe this is a simple fix; to actually follow the specification set forth in the man page, don't treat symbols in a RECURSIVE namespace as if they are saved in resolve.c (apply_default_init_local):

2014-08-29  Fritz Reese  <Reese-Fritz@zai.com>

    * resolve.c (apply_default_init_local): Don't treat variables in
    RECURSIVE units as saved.


diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 43eb240..a428633 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -11104,6 +11104,7 @@ apply_default_init_local (gfc_symbol *sym)
      result variable, which are also nonstatic.  */
   if (sym->attr.save || sym->ns->save_all
       || (gfc_option.flag_max_stack_var_size == 0 && !sym->attr.result
+          && !sym->ns->proc_name->attr.recursive
          && (!sym->attr.dimension || !is_non_constant_shape_array (sym))))
     {
       /* Don't clobber an existing initializer!  */
diff --git a/gcc/testsuite/gfortran.dg/auto_save_2.f90 b/gcc/testsuite/gfortran.
new file mode 100644
index 0000000..0d39d48
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/auto_save_2.f90
@@ -0,0 +1,52 @@
+! { dg-do run }
+! { dg-options "-fno-automatic -finit-local-zero" }
+!
+! Make sure variables are saved with -fno-automatic except in
+! functions marked RECURSIVE, and that they are still initialized with
+! -finit-local-zero.
+!
+
+function f (x)
+implicit none
+  integer f, x
+  integer a ! should be SAVEd
+  a = a + x ! should increment by y every time
+  f = a
+  return
+endfunction
+
+recursive function g (x)
+implicit none
+  integer g, x
+  integer b ! should be automatic
+  b = b + x ! should be set to y every time
+  g = b
+  return
+endfunction
+
+implicit none
+integer f, g
+
+! Should return static value of a; accumulates y
+if ( f(3) .ne. 3 ) then
+  call abort ()
+endif
+if ( f(4) .ne. 7 ) then
+  call abort ()
+endif
+if ( f(2) .ne. 9 ) then
+  call abort ()
+endif
+
+! Should return automatic value of a; equal to y each time
+if ( g(3) .ne. 3 ) then
+  call abort ()
+endif
+if ( g(4) .ne. 4 ) then
+  call abort ()
+endif
+if ( g(2) .ne. 2 ) then
+  call abort ()
+endif
+
+end
Comment 2 Tobias Burnus 2014-08-31 22:29:02 UTC
Author: burnus
Date: Sun Aug 31 22:28:30 2014
New Revision: 214771

URL: https://gcc.gnu.org/viewcvs?rev=214771&root=gcc&view=rev
Log:
2014-08-31  Fritz Reese  <Reese-Fritz@zai.com>

        PR fortran/62309
        * resolve.c (apply_default_init_local): Don't treat variables
        in RECURSIVE procedures as saved.

2014-08-31  Fritz Reese  <Reese-Fritz@zai.com>
            Tobias Burnus  <burnus@net-b.de>

        PR fortran/62309
        * gcc/testsuite/gfortran.dg/auto_save_2.f90: New.


Added:
    trunk/gcc/testsuite/gfortran.dg/auto_save_2.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/resolve.c
    trunk/gcc/testsuite/ChangeLog
Comment 3 Tobias Burnus 2014-08-31 22:31:54 UTC
FIXED on the trunk (GCC 5, which will be released in spring 2015).