re PR fortran/54301 (Add optional warning if pointer assigning a local variable to a nonlocal pointer)

2012-08-20  Tobias Burnus  <burnus@net-b.de>

        PR fortran/54301
        * expr.c (gfc_check_pointer_assign): Warn when the pointer
        might outlive its target.
        * gfortran.h (struct gfc_option_t): Add warn_target_lifetime.
        * options.c (gfc_init_options, set_wall, gfc_handle_option):
        handle it.
        * invoke.texi (-Wtarget-lifetime): Document it.
        (-Wall): Implied it.
        * lang.opt (-Wtarget-lifetime): New flag.

2012-08-20  Tobias Burnus  <burnus@net-b.de>

        PR fortran/54301
        * gfortran.dg/warn_target_lifetime_1.f90: New.

From-SVN: r190522

gcc/fortran/ChangeLog

@@ -1,3 +1,15 @@
+2012-08-20  Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/54301
+	* expr.c (gfc_check_pointer_assign): Warn when the pointer
+	might outlive its target.
+	* gfortran.h (struct gfc_option_t): Add warn_target_lifetime.
+	* options.c (gfc_init_options, set_wall, gfc_handle_option):
+	handle it.
+	* invoke.texi (-Wtarget-lifetime): Document it.
+	(-Wall): Implied it.
+	* lang.opt (-Wtarget-lifetime): New flag.
+
 2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>
 
 	PR fortran/54298

gcc/fortran/expr.c

@@ -3659,6 +3659,38 @@ gfc_check_pointer_assign (gfc_expr *lvalue, gfc_expr *rvalue)
 	  }
     }
 
+  /* Warn if it is the LHS pointer may lives longer than the RHS target.  */
+  if (gfc_option.warn_target_lifetime
+      && rvalue->expr_type == EXPR_VARIABLE
+      && !rvalue->symtree->n.sym->attr.save
+      && !attr.pointer && !rvalue->symtree->n.sym->attr.host_assoc
+      && !rvalue->symtree->n.sym->attr.in_common
+      && !rvalue->symtree->n.sym->attr.use_assoc
+      && !rvalue->symtree->n.sym->attr.dummy)
+    {
+      bool warn;
+      gfc_namespace *ns;
+
+      warn = lvalue->symtree->n.sym->attr.dummy
+	     || lvalue->symtree->n.sym->attr.result
+	     || lvalue->symtree->n.sym->attr.host_assoc
+	     || lvalue->symtree->n.sym->attr.use_assoc
+	     || lvalue->symtree->n.sym->attr.in_common;
+
+      if (rvalue->symtree->n.sym->ns->proc_name
+	  && rvalue->symtree->n.sym->ns->proc_name->attr.flavor != FL_PROCEDURE
+	  && rvalue->symtree->n.sym->ns->proc_name->attr.flavor != FL_PROGRAM)
+       for (ns = rvalue->symtree->n.sym->ns;
+	    ns->proc_name && ns->proc_name->attr.flavor != FL_PROCEDURE;
+	    ns = ns->parent)
+	if (ns->parent == lvalue->symtree->n.sym->ns)
+	  warn = true;
+
+      if (warn)
+	gfc_warning ("Pointer at %L in pointer assignment might outlive the "
+		     "pointer target", &lvalue->where);
+    }
+
   return SUCCESS;
 }
 

gcc/fortran/gfortran.h

@@ -2226,6 +2226,7 @@ typedef struct
   int warn_realloc_lhs;
   int warn_realloc_lhs_all;
   int warn_compare_reals;
+  int warn_target_lifetime;
   int max_errors;
 
   int flag_all_intrinsics;

gcc/fortran/invoke.texi

@@ -147,7 +147,7 @@ and warnings}.
 -Wimplicit-procedure -Wintrinsic-shadow -Wintrinsics-std @gol
 -Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant @gol
 -Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs Wrealloc-lhs-all @gol
--fmax-errors=@var{n} -fsyntax-only -pedantic -pedantic-errors
+-Wtarget-lifetime -fmax-errors=@var{n} -fsyntax-only -pedantic -pedantic-errors
 }
 
 @item Debugging Options
@@ -729,8 +729,8 @@ we recommend avoiding and that we believe are easy to avoid.
 This currently includes @option{-Waliasing}, @option{-Wampersand},
 @option{-Wconversion}, @option{-Wcompare-reals}, @option{-Wsurprising},
 @option{-Wintrinsics-std}, @option{-Wno-tabs}, @option{-Wintrinsic-shadow},
-@option{-Wline-truncation}, @option{-Wreal-q-constant} and
-@option{-Wunused}.
+@option{-Wline-truncation}, @option{-Wtarget-lifetime},
+@option{-Wreal-q-constant} and @option{-Wunused}.
 
 @item -Waliasing
 @opindex @code{Waliasing}
@@ -941,6 +941,11 @@ allocatable variable; this includes scalars and derived types.
 Warn when comparing real or complex types for equality or inequality.
 Enabled by @option{-Wall}.
 
+@item -Wtarget-lifetime
+@opindex @code{Wtargt-lifetime}
+Warn if the pointer in a pointer assignment might be longer than the its
+target. This option is implied by @option{-Wall}.
+
 @item -Werror
 @opindex @code{Werror}
 @cindex warnings, to errors

gcc/fortran/lang.opt

@@ -262,6 +262,10 @@ Wrealloc-lhs-all
 Fortran Warning
 Warn when a left-hand-side variable is reallocated
 
+Wtarget-lifetime
+Fortran Warning
+Warn if the pointer in a pointer assignment might outlive its target
+
 Wreturn-type
 Fortran Warning
 ; Documented in C

gcc/fortran/options.c

@@ -114,6 +114,7 @@ gfc_init_options (unsigned int decoded_options_count,
   gfc_option.warn_realloc_lhs = 0;
   gfc_option.warn_realloc_lhs_all = 0;
   gfc_option.warn_compare_reals = 0;
+  gfc_option.warn_target_lifetime = 0;
   gfc_option.max_errors = 25;
 
   gfc_option.flag_all_intrinsics = 0;
@@ -475,6 +476,7 @@ set_Wall (int setting)
   gfc_option.warn_real_q_constant = setting;
   gfc_option.warn_unused_dummy_argument = setting;
   gfc_option.warn_compare_reals = setting;
+  gfc_option.warn_target_lifetime = setting;
 
   warn_return_type = setting;
   warn_switch = setting;
@@ -688,6 +690,10 @@ gfc_handle_option (size_t scode, const char *arg, int value,
       gfc_option.warn_tabs = value;
       break;
 
+    case OPT_Wtarget_lifetime:
+      gfc_option.warn_target_lifetime = value;
+      break;
+
     case OPT_Wunderflow:
       gfc_option.warn_underflow = value;
       break;

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2012-08-20  Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/54301
+	* gfortran.dg/warn_target_lifetime_1.f90: New.
+
 2012-08-19  Thomas König  <tkoenig@gcc.gnu.org>
 
 	PR fortran/54298

gcc/testsuite/gfortran.dg/warn_target_lifetime_1.f90

@@ -0,0 +1,47 @@
+! { dg-do compile }
+! { dg-options "-Wtarget-lifetime" }
+!
+! PR fortran/54301
+!
+function f () result (ptr)
+  integer, pointer :: ptr(:)
+  integer, allocatable, target :: a(:)
+  allocate(a(5))
+
+  ptr => a ! { dg-warning "Pointer at .1. in pointer assignment might outlive the pointer target" }
+  a = [1,2,3,4,5]
+end function
+
+
+subroutine foo()
+  integer, pointer :: ptr(:)
+  call bar ()
+contains
+  subroutine bar ()
+    integer, target :: tgt(5)
+    ptr => tgt ! { dg-warning "Pointer at .1. in pointer assignment might outlive the pointer target" }
+  end subroutine bar
+end subroutine foo
+
+function foo3(tgt)
+  integer, target :: tgt
+  integer, pointer :: foo3
+  foo3 => tgt
+end function
+
+subroutine sub()
+  implicit none
+  integer, pointer :: ptr
+  integer, target :: tgt
+  ptr => tgt
+
+  block
+    integer, pointer :: p2
+    integer, target :: tgt2
+    p2 => tgt2
+    p2 => tgt
+    ptr => p2
+    ptr => tgt
+    ptr => tgt2 ! { dg-warning "Pointer at .1. in pointer assignment might outlive the pointer target" }
+  end block
+end subroutine sub