(C++) tweak to build_conditional_expr

[Jason Merrill <jason at redhat dot com>]

The lvalue-to-rvalue conversion can fail for a class that cannot be
copied; this patch prevents a crash when that happens.

2000-10-22  Jason Merrill  <jason@redhat.com>

	* call.c (build_conditional_expr): Use ocp_convert to force
	rvalue conversion.

Index: call.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cp/call.c,v
retrieving revision 1.231
diff -c -p -r1.231 call.c
*** call.c	2000/09/19 03:26:11	1.231
--- call.c	2000/10/22 20:20:24
*************** build_conditional_expr (arg1, arg2, arg3
*** 3036,3051 ****
       We need to force the lvalue-to-rvalue conversion here for class types,
       so we get TARGET_EXPRs; trying to deal with a COND_EXPR of class rvalues
       that isn't wrapped with a TARGET_EXPR plays havoc with exception
!      regions.  */
  
    if (IS_AGGR_TYPE (TREE_TYPE (arg2)) && real_lvalue_p (arg2))
!     arg2 = build_user_type_conversion (TREE_TYPE (arg2), arg2, LOOKUP_NORMAL);
    else
      arg2 = decay_conversion (arg2);
    arg2_type = TREE_TYPE (arg2);
  
    if (IS_AGGR_TYPE (TREE_TYPE (arg3)) && real_lvalue_p (arg3))
!     arg3 = build_user_type_conversion (TREE_TYPE (arg3), arg3, LOOKUP_NORMAL);
    else
      arg3 = decay_conversion (arg3);
    arg3_type = TREE_TYPE (arg3);
--- 3036,3056 ----
       We need to force the lvalue-to-rvalue conversion here for class types,
       so we get TARGET_EXPRs; trying to deal with a COND_EXPR of class rvalues
       that isn't wrapped with a TARGET_EXPR plays havoc with exception
!      regions.
  
+      We use ocp_convert rather than build_user_type_conversion because the
+      latter returns NULL_TREE on failure, while the former gives an error.  */
+ 
    if (IS_AGGR_TYPE (TREE_TYPE (arg2)) && real_lvalue_p (arg2))
!     arg2 = ocp_convert (TREE_TYPE (arg2), arg2,
! 			CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
    else
      arg2 = decay_conversion (arg2);
    arg2_type = TREE_TYPE (arg2);
  
    if (IS_AGGR_TYPE (TREE_TYPE (arg3)) && real_lvalue_p (arg3))
!     arg3 = ocp_convert (TREE_TYPE (arg3), arg3,
! 			CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
    else
      arg3 = decay_conversion (arg3);
    arg3_type = TREE_TYPE (arg3);
Index: ../testsuite/g++.old-deja/g++.other/volatile1.C
===================================================================
RCS file: volatile1.C
diff -N volatile1.C
*** /dev/null	Tue May  5 13:32:27 1998
--- ../testsuite/g++.old-deja/g++.other/volatile1.C	Sun Oct 22 13:20:24 2000
***************
*** 0 ****
--- 1,19 ----
+ // Test that failed lvalue-to-rvalue conversion of vf doesn't crash the
+ // compiler.
+ 
+ class f_class
+ { };				// ERROR - candidates
+ 
+ volatile f_class
+ ret_v_f_class()
+ {
+   f_class t;
+   return t;
+ }
+ 
+ int main(void)
+ {
+   volatile f_class vf;
+   0 ? ret_v_f_class() : vf;	// ERROR - can't copy volatile lvalue
+   return 0;
+ }