[Discuss-gnuradio] make check failure and solution patch (faulty gr_basic_block sort in gr_flow_graph)

[Martin Dvh]

Hi All,
This patch makes the sort of basic_blocks reliable in gr_flowgraph.cc
Without it make check can fail in qa_gr_flowgraph.cc:240

background:
While working with new buffer code I found that make check can fail in 
qa_gr_flowgraph.cc
240:  CPPUNIT_ASSERT(graphs[0].size() == 4);

The cause of this is that the subgraphs are not in the order as expected.
The code expects
graphs.size()==3
graphs[0].size()==4
graphs[1].size()==3
graphs[2].size()==2

But it gets
graphs.size()==3
graphs[0].size()==3
graphs[1].size()==2
graphs[2].size()==4

This only happens if there are a lot of big malloc /frees in code before it.
The probable cause is that a plain std::sort is used for sorting vectors of 
gr_basic_block
But for gr_basic_block the operator < is not defined.

I changed the code to use basic_block->unique_id() for sorting.
This should be more robust.

(I got rid of the make check failure)
This problem might be in more parts of the code


Greetings,
Martin

Index: gr_flowgraph.cc
===================================================================
--- gr_flowgraph.cc     (revision 9229)
+++ gr_flowgraph.cc     (working copy)
@@ -30,6 +30,11 @@
 #include <sstream>

 #define GR_FLOWGRAPH_DEBUG 0
+bool
+basic_block_sort_predicate(const gr_basic_block_sptr lhs, const 
gr_basic_block_sptr rhs)
+{
+  return lhs->unique_id() < rhs->unique_id();
+}

 gr_edge::~gr_edge()
 {
@@ -173,7 +178,8 @@
   }

   // Return vector of unique blocks
-  sort(tmp.begin(), tmp.end());
+  //sort(tmp.begin(), tmp.end());
+  sort(tmp.begin(), tmp.end(),basic_block_sort_predicate);
   unique_copy(tmp.begin(), tmp.end(), inserter);
   return result;
 }
@@ -272,7 +278,7 @@
       tmp.push_back(p->dst().block());

   // Remove duplicates
-  sort(tmp.begin(), tmp.end());
+  sort(tmp.begin(), tmp.end(),basic_block_sort_predicate);
   unique_copy(tmp.begin(), tmp.end(), inserter);
   return result;
 }
@@ -288,7 +294,7 @@
       tmp.push_back(p->dst().block());

   // Remove duplicates
-  sort(tmp.begin(), tmp.end());
+  sort(tmp.begin(), tmp.end(),basic_block_sort_predicate);
   unique_copy(tmp.begin(), tmp.end(), inserter);
   return result;
 }
@@ -399,7 +405,7 @@
   }

   // Remove duplicates
-  sort(tmp.begin(), tmp.end());
+  sort(tmp.begin(), tmp.end(),basic_block_sort_predicate);
   unique_copy(tmp.begin(), tmp.end(), inserter);
   return result;
 }