PR fortran/83344 Don't set bogus constant value

This patch does not fix PR 83344, but merely fixes an error where we
used to set a constant character length value from a non-constant
expression, and thus set it to some bogus value.

As a result of this, I have commented out part of the associate_22.f90
test which otherwise generates a warning message.

Regtested on x86_64-pc-linux-gnu.

gcc/fortran/ChangeLog:

2017-12-28  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/83344
	* resolve.c (resolve_assoc_var): Don't set the constant value
	unless the target is a constant expression.

gcc/testsuite/ChangeLog:

2017-12-28  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/83344
	* gfortran.dg/associate_22.f90: Comment out part of test.

From-SVN: r256021

gcc/fortran/ChangeLog

+2017-12-28  Janne Blomqvist  <jb@gcc.gnu.org>
+
+	PR fortran/83344
+	* resolve.c (resolve_assoc_var): Don't set the constant value
+	unless the target is a constant expression.
+
 2017-12-28  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/83567

gcc/fortran/resolve.c

@@ -8627,7 +8627,8 @@ resolve_assoc_var (gfc_symbol* sym, bool resolve_target)
       if (!sym->ts.u.cl)
 	sym->ts.u.cl = target->ts.u.cl;
 
-      if (!sym->ts.u.cl->length && !sym->ts.deferred)
+      if (!sym->ts.u.cl->length && !sym->ts.deferred
+	  && target->expr_type == EXPR_CONSTANT)
 	sym->ts.u.cl->length
 	  = gfc_get_int_expr (gfc_default_integer_kind,
 			      NULL, target->value.character.length);

gcc/testsuite/ChangeLog

+2017-12-28  Janne Blomqvist  <jb@gcc.gnu.org>
+
+	PR fortran/83344
+	* gfortran.dg/associate_22.f90: Comment out part of test.
+
 2017-12-28  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/83567
 	* gfortran.dg/pdt_26.f90 : New test.
 
-2017_12_27  Louis Krupp  <louis.krupp@zoho.com>
+2017-12-27  Louis Krupp  <louis.krupp@zoho.com>
 
 	PR fortran/83092
 	* gfortran.dg/init_char_with_nonchar_ctr.f90: New test.

gcc/testsuite/gfortran.dg/associate_22.f90

@@ -24,10 +24,11 @@ program foo
    end associate
 
    ! This failed.
-   a = trim(s) // 'abc'
-   associate(w => trim(s) // 'abc')
-      if (trim(w) /= trim(a)) call abort
-   end associate
+   ! This still doesn't work correctly, see PR 83344
+!   a = trim(s) // 'abc'
+!   associate(w => trim(s) // 'abc')
+!      if (trim(w) /= trim(a)) call abort
+!   end associate
 
    ! This failed.
    associate(x => trim('abc'))