From: Mark Mitchell <mark@codesourcery.com>
Date: Mon, 13 Aug 2001 21:07:22 +0000 (+0000)
Subject: call.c (build_over_call): Mark COMPOUND_EXPRs generated for empty class assignment... 
X-Git-Tag: prereleases/libstdc++-3.0.95~2672
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=63d6f87a6d1eae6411542567d6834c27c4509f40;p=thirdparty%2Fgcc.git

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
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index b5f90a07ec7e..f49263b28130 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 6278095b8348..8203032fc8ad 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);
diff --git a/gcc/testsuite/g++.old-deja/g++.other/empty2.C b/gcc/testsuite/g++.old-deja/g++.other/empty2.C
new file mode 100644
index 000000000000..92585b8b03f2
--- /dev/null
+++ b/gcc/testsuite/g++.old-deja/g++.other/empty2.C
@@ -0,0 +1,10 @@
+// Build don't link:
+// Origin: Mark Mitchell <mark@codesourcery.com>
+
+struct E {};
+
+void f () {
+  E e1, e2;
+  e1 = e2; // We should not warn about this statement, even though no
+           // code is generated for it.
+}