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[PATCH] PR fortran/78739 -- detect statement function name conflict


The attach patch checks that a statement function name
does not conflict the name of the containing function.
Regression tested on x86_64-*-freebsd.  OK to commit?

2019-08-16  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/78739
	* match.c (gfc_match_st_function):  When matching a statement function,
	need to check if the statement function name shadows the function
	name.

2019-08-16  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/78739
	* fortran.dg/pr78739.f90: New test.

-- 
Steve
Index: gcc/fortran/match.c
===================================================================
--- gcc/fortran/match.c	(revision 274578)
+++ gcc/fortran/match.c	(working copy)
@@ -5751,7 +5751,29 @@ gfc_match_st_function (void)
   gfc_symbol *sym;
   gfc_expr *expr;
   match m;
+  char name[GFC_MAX_SYMBOL_LEN + 1];
+  locus old_locus;
+  bool fcn;
+  gfc_formal_arglist *ptr;
 
+  /* Read the possible statement function name, and then check to see if
+     a symbol is already present in the namespace.  Record if it is a
+     function and whether it has been referenced.  */
+  fcn = false;
+  ptr = NULL;
+  old_locus = gfc_current_locus;
+  m = gfc_match_name (name);
+  if (m == MATCH_YES)
+    {
+      gfc_find_symbol (name, NULL, 1, &sym);
+      if (sym && sym->attr.function && !sym->attr.referenced)
+	{
+	  fcn = true;
+	  ptr = sym->formal;
+	}
+    }
+
+  gfc_current_locus = old_locus;
   m = gfc_match_symbol (&sym, 0);
   if (m != MATCH_YES)
     return m;
@@ -5776,6 +5798,13 @@ gfc_match_st_function (void)
   if (recursive_stmt_fcn (expr, sym))
     {
       gfc_error ("Statement function at %L is recursive", &expr->where);
+      return MATCH_ERROR;
+    }
+
+  if (fcn && ptr != sym->formal)
+    {
+      gfc_error ("Statement function %qs at %L conflicts with function name",
+		 sym->name, &expr->where);
       return MATCH_ERROR;
     }
 
Index: gcc/testsuite/gfortran.dg/pr78739.f90
===================================================================
--- gcc/testsuite/gfortran.dg/pr78739.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/pr78739.f90	(working copy)
@@ -0,0 +1,15 @@
+! { dg-do compile }
+! { dg-options "-w" }
+! PR fortran/78739
+! Code contributed Gerhard Steinmetz
+function f(n)
+   f() = n    ! { dg-error "conflicts with function name" }
+end
+
+function g()
+   g(x) = x   ! { dg-error "conflicts with function name" }
+end
+
+function a()  ! This should cause an error, but cannot be easily detected!
+   a() = x
+end

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