[analyzer] Add more info to exploded graph dumps

[NoQ]

Summary

debug.ViewExplodedGraph, aka -analyzer-viz-egraph-graphviz, is often the only way to understand the otherwise confusing analyzer report. Exploded graphs are often heavy (see also -trim-egraph) and hard to navigate (especially when using a specialized .dot-file viewer like xdot - i found it much more comfortable to convert the file to .svg and view in a web browser), and it often takes many hours to figure out what peculiar path has the analyzer found or what particular thing about the program he doesn't understand.

While it is clear that everybody's desire is to provide the information about reports to the user in a more friendly manner, i've made a quick patch that adds an explanation of location contexts to the dumps. Not only such info would help the developer understand what location context is (it's far from obvious), but also i find it extremely convenient to quickly understand "what are we analyzing here" by looking at any node of the graph, which simplifies navigation dramatically for me.

Perhaps we could add more useful info? I'm also thinking of simplifying store and environment dumps for easier reading and less size, eg. mention every cluster or location context only once rather than on every line.

This patch removes some of the surrounding dead code, because the FIXMEs have already been addressed by introducing checker name tags and visitors.

[NoQ]

Whoops forgot the screenshots:

Also not sure how to write tests for these, because we can't choose the directory path for the dump, can we?

[zaks.anna]

Great!

How does this work when a path spans multiple files, specifically, when the definitions from a header file are inlined? We could add file names but only in cases the file name does not match the main file.

and hard to navigate (especially when using a specialized .dot-file viewer like xdot - i found it
much more comfortable to convert the file to .svg and view in a web browser

This is not something that the patch addresses. Feel free to add a patch to the checker developer manual with instructions for this.

[NoQ]

We could add file names but only in cases the file name does not match the main file.

Whoops, right, i guess i'd just fall back to the default source location printing routine for this case (or for macros).

This is not something that the patch addresses.

Yeah, just since we're all here anyway... By the way, -analyzer-config prune-paths=false is also very handy.

[zaks.anna]

Yeah, just since we're all here anyway... By the way, -analyzer-config prune-paths=false is also very handy.

I think you should add these to the checker writer manual in the debugging section.

lib/StaticAnalyzer/Core/ExprEngine.cpp

 struct DOTGraphTraits<ExplodedNode*> :
   public DefaultDOTGraphTraits {
 
   DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
 
   // FIXME: Since we do not cache error nodes in ExprEngine now, this does not
   // work.
   static std::string getNodeAttributes(const ExplodedNode *N, void*) {
-
-#if 0
-      // FIXME: Replace with a general scheme to tell if the node is
-      // an error node.
-    if (GraphPrintCheckerState->isImplicitNullDeref(N) ||
-        GraphPrintCheckerState->isExplicitNullDeref(N) ||
-        GraphPrintCheckerState->isUndefDeref(N) ||
-        GraphPrintCheckerState->isUndefStore(N) ||
-        GraphPrintCheckerState->isUndefControlFlow(N) ||
-        GraphPrintCheckerState->isUndefResult(N) ||
-        GraphPrintCheckerState->isBadCall(N) ||
-        GraphPrintCheckerState->isUndefArg(N))
-      return "color=\"red\",style=\"filled\"";
-
-    if (GraphPrintCheckerState->isNoReturnCall(N))
-      return "color=\"blue\",style=\"filled\"";
-#endif
     return "";
   }
 
   static void printLocation(raw_ostream &Out, SourceLocation SLoc) {
     if (SLoc.isFileID()) {
       Out << "\\lline="
         << GraphPrintSourceManager->getExpansionLineNumber(SLoc)
         << " col="
static std::string getNodeLabel(const ExplodedNode *N, void*){
 
     // Program Location.
     ProgramPoint Loc = N->getLocation();
 
     switch (Loc.getKind()) {
       case ProgramPoint::BlockEntranceKind: {
         Out << "Block Entrance: B"
             << Loc.castAs<BlockEntrance>().getBlock()->getBlockID();
-        if (const NamedDecl *ND =
-                    dyn_cast<NamedDecl>(Loc.getLocationContext()->getDecl())) {
-          Out << " (";
-          ND->printName(Out);
-          Out << ")";
-        }
         break;
       }
 
       case ProgramPoint::BlockExitKind:
         assert (false);
         break;
 
       case ProgramPoint::CallEnterKind:
switch (Loc.getKind()) {
               Out << "true";
             else
               Out << "false";
           }
 
           Out << "\\l";
         }
 
-#if 0
-          // FIXME: Replace with a general scheme to determine
-          // the name of the check.
-        if (GraphPrintCheckerState->isUndefControlFlow(N)) {
-          Out << "\\|Control-flow based on\\lUndefined value.\\l";
-        }
-#endif
         break;
       }
 
       default: {
         const Stmt *S = Loc.castAs<StmtPoint>().getStmt();
         assert(S != nullptr && "Expecting non-null Stmt");
 
         Out << S->getStmtClassName() << ' ' << (const void*) S << ' ';
         LangOptions LO; // FIXME.
         S->printPretty(Out, nullptr, PrintingPolicy(LO));
         printLocation(Out, S->getLocStart());
 
         if (Loc.getAs<PreStmt>())
           Out << "\\lPreStmt\\l;";
         else if (Loc.getAs<PostLoad>())
           Out << "\\lPostLoad\\l;";
         else if (Loc.getAs<PostStore>())
           Out << "\\lPostStore\\l";
         else if (Loc.getAs<PostLValue>())
           Out << "\\lPostLValue\\l";
 
-#if 0
-          // FIXME: Replace with a general scheme to determine
-          // the name of the check.
-        if (GraphPrintCheckerState->isImplicitNullDeref(N))
-          Out << "\\|Implicit-Null Dereference.\\l";
-        else if (GraphPrintCheckerState->isExplicitNullDeref(N))
-          Out << "\\|Explicit-Null Dereference.\\l";
-        else if (GraphPrintCheckerState->isUndefDeref(N))
-          Out << "\\|Dereference of undefialied value.\\l";
-        else if (GraphPrintCheckerState->isUndefStore(N))
-          Out << "\\|Store to Undefined Loc.";
-        else if (GraphPrintCheckerState->isUndefResult(N))
-          Out << "\\|Result of operation is undefined.";
-        else if (GraphPrintCheckerState->isNoReturnCall(N))
-          Out << "\\|Call to function marked \"noreturn\".";
-        else if (GraphPrintCheckerState->isBadCall(N))
-          Out << "\\|Call to NULL/Undefined.";
-        else if (GraphPrintCheckerState->isUndefArg(N))
-          Out << "\\|Argument in call is undefined";
-#endif
-
         break;
       }
     }
 
     ProgramStateRef state = N->getState();
     Out << "\\|StateID: " << (const void*) state.get()
         << " NodeID: " << (const void*) N << "\\|";
+
+    // Analysis stack backtrace.
+    Out << "Location context stack (from current to outer):\\l";
+    const LocationContext *LC = Loc.getLocationContext();
+    unsigned Idx = 0;
+    for (; LC; LC = LC->getParent(), ++Idx) {
+      Out << Idx << ". (" << (const void *)LC << ") ";
+      switch (LC->getKind()) {
+      case LocationContext::StackFrame:
+        if (const NamedDecl *D = dyn_cast<NamedDecl>(LC->getDecl()))
+          Out << "Calling " << D->getQualifiedNameAsString();
+        else
+          Out << "Calling anonymous code";
+        if (const Stmt *S = cast<StackFrameContext>(LC)->getCallSite()) {
+          SourceLocation SiteLoc = S->getLocStart();
+          if (SiteLoc.isFileID()) {
+            Out << " at line "
+                << GraphPrintSourceManager->getExpansionLineNumber(SiteLoc);
+          }
+        }
+        break;
+      case LocationContext::Block:
+        Out << "Invoking block";
+        if (const Decl *D = cast<BlockInvocationContext>(LC)->getBlockDecl()) {
+          SourceLocation DefLoc = D->getLocStart();
+          if (DefLoc.isFileID()) {
+            Out << " defined at line "
+                << GraphPrintSourceManager->getExpansionLineNumber(DefLoc);
+          }
+        }
+        break;
+      case LocationContext::Scope:
+        Out << "Entering scope";
+        // FIXME: Add more info once ScopeContext is activated.
+        break;
+      }
+      Out << "\\l";
+    }
+    Out << "\\l";
+
     state->printDOT(Out);
 
     Out << "\\l";
 
     if (const ProgramPointTag *tag = Loc.getTag()) {
       Out << "\\|Tag: " << tag->getTagDescription();
       Out << "\\l";
     }