Fix escape analysis

has_value was previously constant true.

Author: tautschnig

regression/goto-instrument/show-escape-analysis1/main.c

@@ -0,0 +1,13 @@
+#include <stdlib.h>
+
+void foo()
+{
+  int *leaked1=malloc(sizeof(int));
+  int *leaked2=malloc(sizeof(int));
+}
+
+int main()
+{
+  foo();
+  return 0;
+}

regression/goto-instrument/show-escape-analysis1/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+--show-escape-analysis
+^EXIT=0$
+^SIGNAL=0$
+^Aliases:.*(malloc.*leaked|leaked.*malloc)
+--
+^warning: ignoring

src/analyses/escape_analysis.cpp

@@ -305,16 +305,8 @@ bool escape_domaint::merge(
   locationt from,
   locationt to)
 {
-  if(b.has_values.is_false())
-    return false; // no change
-
-  if(has_values.is_false())
-  {
-    *this=b;
-    return true; // change
-  }
-
-  bool changed=false;
+  bool changed=has_values.is_false();
+  has_values=tvt::unknown();
 
   for(const auto &cleanup : b.cleanup_map)
   {