Fixed bug in the cutting of back edges (that manifested itself whenever the first block in a procedure was the target of a back edge)

2 files changed, 34 insertions, 1 deletions

diff --git a/Test/test2/Answer b/Test/test2/Answer
index 4a7fd32f..b936ef87 100644
--- a/Test/test2/Answer
+++ b/Test/test2/Answer
@@ -153,8 +153,15 @@ CutBackEdge.bpl(10,5): Error BP5005: This loop invariant might not be maintained
 Execution trace:

     CutBackEdge.bpl(5,3): entry

     CutBackEdge.bpl(9,3): block850

+CutBackEdge.bpl(20,5): Error BP5004: This loop invariant might not hold on entry.

+Execution trace:

+CutBackEdge.bpl(26,5): Error BP5001: This assertion might not hold.

+Execution trace:

+    CutBackEdge.bpl(25,3): L

+CutBackEdge.bpl(38,5): Error BP5004: This loop invariant might not hold on entry.

+Execution trace:

 

-Boogie program verifier finished with 0 verified, 1 error

+Boogie program verifier finished with 1 verified, 4 errors

 

 -------------------- False.bpl --------------------

 

diff --git a/Test/test2/CutBackEdge.bpl b/Test/test2/CutBackEdge.bpl
index 934974aa..7294d0f9 100644
--- a/Test/test2/CutBackEdge.bpl
+++ b/Test/test2/CutBackEdge.bpl
@@ -12,3 +12,29 @@ procedure Test()
     goto block850;

 

 }

+

+// The following procedure once exhibited a bug in Boogie's DAG manipulations

+procedure TightLoop0()

+{

+  L:

+    assert !true;  // error

+    goto L;

+}

+procedure TightLoop1()

+{

+  L:

+    assert false;  // error

+    goto L;

+}

+procedure TightLoop2()

+{

+  L:

+    assert true;  // cool

+    goto L;

+}

+procedure TightLoop3(b: bool)

+{

+  L:

+    assert b;  // error

+    goto L;

+}