[analyzer] Add explanation why analyzer report is not generated (fix for PR12421).

Currently if the path diagnostic consumer (e.g HTMLDiagnostics and PlistDiagnostics) do not support cross file diagnostics then the path diagnostic report is silently omitted in the case of cross file diagnostics. The patch adds a little verbosity to Clang in this case.
The patch also adds help entry for the "--analyzer-output" driver option.

llvm-svn: 283499

clang/include/clang/Driver/Options.td

@@ -2005,7 +2005,8 @@ def _CLASSPATH : Separate<["--"], "CLASSPATH">, Alias<fclasspath_EQ>;
 def _all_warnings : Flag<["--"], "all-warnings">, Alias<Wall>;
 def _analyze_auto : Flag<["--"], "analyze-auto">, Flags<[DriverOption]>;
 def _analyzer_no_default_checks : Flag<["--"], "analyzer-no-default-checks">, Flags<[DriverOption]>;
-def _analyzer_output : JoinedOrSeparate<["--"], "analyzer-output">, Flags<[DriverOption]>;
+def _analyzer_output : JoinedOrSeparate<["--"], "analyzer-output">, Flags<[DriverOption]>,
+  HelpText<"Static analyzer report output format (html|plist|plist-multi-file|plist-html|text).">;
 def _analyze : Flag<["--"], "analyze">, Flags<[DriverOption, CoreOption]>,
   HelpText<"Run the static analyzer">;
 def _assemble : Flag<["--"], "assemble">, Alias<S>;

clang/lib/StaticAnalyzer/Core/PathDiagnostic.cpp

@@ -211,6 +211,12 @@ void PathDiagnosticConsumer::HandlePathDiagnostic(
     const SourceManager &SMgr = D->path.front()->getLocation().getManager();
     SmallVector<const PathPieces *, 5> WorkList;
     WorkList.push_back(&D->path);
+    SmallString<128> buf;
+    llvm::raw_svector_ostream warning(buf);
+    warning << "warning: Path diagnostic report is not generated. Current "
+            << "output format does not support diagnostics that cross file "
+            << "boundaries. Refer to --analyzer-output for valid output "
+            << "formats\n";
 
     while (!WorkList.empty()) {
       const PathPieces &path = *WorkList.pop_back_val();
@@ -222,19 +228,25 @@ void PathDiagnosticConsumer::HandlePathDiagnostic(
 
         if (FID.isInvalid()) {
           FID = SMgr.getFileID(L);
-        } else if (SMgr.getFileID(L) != FID)
-          return; // FIXME: Emit a warning?
+        } else if (SMgr.getFileID(L) != FID) {
+          llvm::errs() << warning.str();
+          return;
+        }
 
         // Check the source ranges.
         ArrayRef<SourceRange> Ranges = piece->getRanges();
         for (ArrayRef<SourceRange>::iterator I = Ranges.begin(),
                                              E = Ranges.end(); I != E; ++I) {
           SourceLocation L = SMgr.getExpansionLoc(I->getBegin());
-          if (!L.isFileID() || SMgr.getFileID(L) != FID)
-            return; // FIXME: Emit a warning?
+          if (!L.isFileID() || SMgr.getFileID(L) != FID) {
+            llvm::errs() << warning.str();
+            return;
+          }
           L = SMgr.getExpansionLoc(I->getEnd());
-          if (!L.isFileID() || SMgr.getFileID(L) != FID)
-            return; // FIXME: Emit a warning?
+          if (!L.isFileID() || SMgr.getFileID(L) != FID) {
+            llvm::errs() << warning.str();
+            return;
+          }
         }
 
         if (const PathDiagnosticCallPiece *call =

clang/test/Analysis/diagnostics/diag-cross-file-boundaries.c

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core -verify %s
+// RUN: %clang_cc1 -analyze -analyzer-checker=core -analyzer-output=html -o PR12421.html %s 2>&1 | FileCheck %s
+
+// Test for PR12421
+#include "diag-cross-file-boundaries.h"
+
+int main(){
+  f();
+  return 0;
+}
+
+// CHECK: warning: Path diagnostic report is not generated.

clang/test/Analysis/diagnostics/diag-cross-file-boundaries.h

@@ -0,0 +1,4 @@
+static void f() {
+  int *p = 0;
+  *p = 1;       // expected-warning{{Dereference of null pointer}}
+}