[analyzer] Allow suppressing diagnostics reported within the 'std' namespace

This is controlled by the 'suppress-c++-stdlib' analyzer-config flag.
It is currently off by default.

This is more suppression than we'd like to do, since obviously there can
be user-caused issues within 'std', but it gives us the option to wield
a large hammer to suppress false positives the user likely can't work
around.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178513 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/StaticAnalyzer/Core/AnalyzerOptions.h

@@ -217,6 +217,9 @@ private:
   /// \sa shouldSuppressInlinedDefensiveChecks
   Optional<bool> SuppressInlinedDefensiveChecks;
 
+  /// \sa shouldSuppressFromCXXStandardLibrary
+  Optional<bool> SuppressFromCXXStandardLibrary;
+
   /// \sa getGraphTrimInterval
   Optional<unsigned> GraphTrimInterval;
 
@@ -306,6 +309,13 @@ public:
   /// option, which accepts the values "true" and "false".
   bool shouldSuppressInlinedDefensiveChecks();
 
+  /// Returns whether or not diagnostics reported within the C++ standard
+  /// library should be suppressed.
+  ///
+  /// This is controlled by the 'suppress-c++-stdlib' config option,
+  /// which accepts the values "true" and "false".
+  bool shouldSuppressFromCXXStandardLibrary();
+
   /// Returns whether irrelevant parts of a bug report path should be pruned
   /// out of the final output.
   ///

lib/StaticAnalyzer/Core/AnalyzerOptions.cpp

@@ -158,6 +158,12 @@ bool AnalyzerOptions::shouldSuppressInlinedDefensiveChecks() {
                           /* Default = */ true);
 }
 
+bool AnalyzerOptions::shouldSuppressFromCXXStandardLibrary() {
+  return getBooleanOption(SuppressFromCXXStandardLibrary,
+                          "suppress-c++-stdlib",
+                          /* Default = */ false);
+}
+
 int AnalyzerOptions::getOptionAsInteger(StringRef Name, int DefaultVal) {
   SmallString<10> StrBuf;
   llvm::raw_svector_ostream OS(StrBuf);

lib/StaticAnalyzer/Core/BugReporterVisitors.cpp

@@ -1421,28 +1421,53 @@ ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
   return event;
 }
 
+
+// FIXME: Copied from ExprEngineCallAndReturn.cpp.
+static bool isInStdNamespace(const Decl *D) {
+  const DeclContext *DC = D->getDeclContext()->getEnclosingNamespaceContext();
+  const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(DC);
+  if (!ND)
+    return false;
+
+  while (const NamespaceDecl *Parent = dyn_cast<NamespaceDecl>(ND->getParent()))
+    ND = Parent;
+
+  return ND->getName() == "std";
+}
+
+
 PathDiagnosticPiece *
 LikelyFalsePositiveSuppressionBRVisitor::getEndPath(BugReporterContext &BRC,
                                                     const ExplodedNode *N,
                                                     BugReport &BR) {
-  const Stmt *S = BR.getStmt();
-  if (!S)
-    return 0;
-
-  // Here we suppress false positives coming from system macros. This list is
+  // Here we suppress false positives coming from system headers. This list is
   // based on known issues.
 
+  // Skip reports within the 'std' namespace. Although these can sometimes be
+  // the user's fault, we currently don't report them very well, and
+  // Note that this will not help for any other data structure libraries, like
+  // TR1, Boost, or llvm/ADT.
+  ExprEngine &Eng = BRC.getBugReporter().getEngine();
+  AnalyzerOptions &Options = Eng.getAnalysisManager().options;
+  if (Options.shouldSuppressFromCXXStandardLibrary()) {
+    const LocationContext *LCtx = N->getLocationContext();
+    if (isInStdNamespace(LCtx->getDecl())) {
+      BR.markInvalid(getTag(), 0);
+      return 0;
+    }
+  }
+
   // Skip reports within the sys/queue.h macros as we do not have the ability to
   // reason about data structure shapes.
   SourceManager &SM = BRC.getSourceManager();
-  SourceLocation Loc = S->getLocStart();
+  FullSourceLoc Loc = BR.getLocation(SM).asLocation();
   while (Loc.isMacroID()) {
     if (SM.isInSystemMacro(Loc) &&
        (SM.getFilename(SM.getSpellingLoc(Loc)).endswith("sys/queue.h"))) {
       BR.markInvalid(getTag(), 0);
       return 0;
     }
-    Loc = SM.getSpellingLoc(Loc);
+    Loc = Loc.getSpellingLoc();
   }
 
   return 0;

test/Analysis/Inputs/system-header-simulator-cxx.h

@@ -73,6 +73,13 @@ namespace std {
   struct nothrow_t {};
 
   extern const nothrow_t nothrow;
+
+  template<class InputIter, class OutputIter>
+  OutputIter copy(InputIter II, InputIter IE, OutputIter OI) {
+    while (II != IE)
+      *OI++ = *II++;
+    return OI;
+  }
 }
 
 void* operator new(std::size_t, const std::nothrow_t&) throw();

test/Analysis/diagnostics/explicit-suppression.cpp

@@ -0,0 +1,71 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.ExprInspection -analyzer-config suppress-c++-stdlib=false -verify %s
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.ExprInspection -analyzer-config suppress-c++-stdlib=true -DSUPPRESSED=1 -verify %s
+
+#ifdef SUPPRESSED
+// expected-no-diagnostics
+#endif
+
+#include "../Inputs/system-header-simulator-cxx.h"
+
+void clang_analyzer_eval(bool);
+
+void testCopyNull(int *I, int *E) {
+  std::copy(I, E, (int *)0);
+#ifndef SUPPRESSED
+  // This line number comes from system-header-simulator-cxx.h.
+  // expected-warning@65 {{Dereference of null pointer}}
+#endif
+}
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+// PR15613: expected-* can't refer to diagnostics in other source files.
+// The current implementation only matches line numbers, but has an upper limit
+// of the number of lines in the main source file.