call.c (build_over_call): Mark COMPOUND_EXPRs generated for empty class assignment as having side-effects...

	* call.c (build_over_call): Mark COMPOUND_EXPRs generated for
	empty class assignment as having side-effects to avoid
	spurious warnings.

From-SVN: r44868

2 files changed, 15 insertions, 0 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b5f90a0..f49263b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2001-08-13  Mark Mitchell  <mark@codesourcery.com>
+
+	* call.c (build_over_call): Mark COMPOUND_EXPRs generated for
+	empty class assignment as having side-effects to avoid
+	spurious warnings.
+
 2001-08-13  Zack Weinberg  <zackw@panix.com>
 
 	* Make-lang.in (cp/except.o): Add libfuncs.h to dependencies.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 6278095..8203032 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4292,6 +4292,15 @@ build_over_call (cand, args, flags)
 	  TREE_USED (arg) = 1;
 
 	  val = build (COMPOUND_EXPR, DECL_CONTEXT (fn), arg, to);
+	  /* Even though the assignment may not actually result in any
+	     code being generated, we do not want to warn about the
+	     assignment having no effect.  That would be confusing to
+	     users who may be performing the assignment as part of a
+	     generic algorithm, for example.
+	     
+	     Ideally, the notions of having side-effects and of being
+	     useless would be orthogonal.  */
+	  TREE_SIDE_EFFECTS (val) = 1;
 	}
       else
 	val = build (MODIFY_EXPR, TREE_TYPE (to), to, arg);