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C++ PATCH for c++/70153 (unhandled UNARY_PLUS_EXPR causes stack overflow)


Here, we got ourselves into infinite recursion in fold, resulting in a stack
overflow.  I believe the crux is that we're passing UNARY_PLUS_EXPR, a C++-only
code, into fold which can't really fold e.g. 1 + UNARY_PLUS_EXPR <1>.  I think
cp_fold should be able to fold this to 2, but currently is not.  But I noticed
that cxx_eval_constant_expression seems to handle this:
        if (tcode == UNARY_PLUS_EXPR)
          r = fold_convert (TREE_TYPE (t), op);
so I tweaked cp_fold to do something similar.  With this patch we're able to
fold the expression above properly and fold doesn't run into infinite looping
anymore.

I made the test a run-time test to sanity-check we're generating the correct
value.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-03-10  Marek Polacek  <polacek@redhat.com>

	PR c++/70153
	* cp-gimplify.c (cp_fold): Handle UNARY_PLUS_EXPR.

	* g++.dg/delayedfold/unary-plus1.C: New test.

diff --git gcc/cp/cp-gimplify.c gcc/cp/cp-gimplify.c
index 6af3760..db23efe 100644
--- gcc/cp/cp-gimplify.c
+++ gcc/cp/cp-gimplify.c
@@ -2009,6 +2009,8 @@ cp_fold (tree x)
 	  else
 	    x = fold_build1_loc (loc, code, TREE_TYPE (x), op0);
 	}
+      else if (code == UNARY_PLUS_EXPR)
+	x = fold_convert (TREE_TYPE (x), op0);
       else
 	x = fold (x);
 
diff --git gcc/testsuite/g++.dg/delayedfold/unary-plus1.C gcc/testsuite/g++.dg/delayedfold/unary-plus1.C
index e69de29..5ebee22 100644
--- gcc/testsuite/g++.dg/delayedfold/unary-plus1.C
+++ gcc/testsuite/g++.dg/delayedfold/unary-plus1.C
@@ -0,0 +1,15 @@
+// PR c++/70153
+// { dg-do run }
+
+unsigned long long int
+foo (unsigned long long int i)
+{
+  return 2ULL * ((1 + (unsigned long int) +1) * i);
+}
+
+int
+main (void)
+{
+  if (foo (3ULL) != 12ULL)
+    __builtin_abort ();
+}

	Marek


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