r256886 - [analyzer] Suppress reports coming from std::__independent_bits_engine

[Anna Zaks via cfe-commits]

Author: zaks
Date: Tue Jan  5 18:32:52 2016
New Revision: 256886

URL: http://llvm.org/viewvc/llvm-project?rev=256886&view=rev
Log:
[analyzer] Suppress reports coming from std::__independent_bits_engine

The analyzer reports a shift by a negative value in the constructor. The bug can
be easily triggered by calling std::random_shuffle on a vector
(<rdar://problem/19658126>).

(The shift by a negative value is reported because __w0_ gets constrained to
63 by the conditions along the path:__w0_ < _WDt && __w0_ >= _WDt-1,
where _WDt is 64. In normal execution, __w0_ is not 63, it is 1 and there is
no overflow. The path is infeasible, but the analyzer does not know about that.)

Modified:
    cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
    cfe/trunk/test/Analysis/Inputs/system-header-simulator-cxx.h
    cfe/trunk/test/Analysis/inlining/stl.cpp

Modified: cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp?rev=256886&r1=256885&r2=256886&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp Tue Jan  5 18:32:52 2016
@@ -1542,6 +1542,16 @@ LikelyFalsePositiveSuppressionBRVisitor:
         }
       }
 
+      // The analyzer issues a false positive when the constructor of
+      // std::__independent_bits_engine from algorithms is used.
+      if (const CXXConstructorDecl *MD = dyn_cast<CXXConstructorDecl>(D)) {
+        const CXXRecordDecl *CD = MD->getParent();
+        if (CD->getName() == "__independent_bits_engine") {
+          BR.markInvalid(getTag(), nullptr);
+          return nullptr;
+        }
+      }
+
       // The analyzer issues a false positive on
       //   std::basic_string<uint8_t> v; v.push_back(1);
       // and

Modified: cfe/trunk/test/Analysis/Inputs/system-header-simulator-cxx.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/Inputs/system-header-simulator-cxx.h?rev=256886&r1=256885&r2=256886&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/Inputs/system-header-simulator-cxx.h (original)
+++ cfe/trunk/test/Analysis/Inputs/system-header-simulator-cxx.h Tue Jan  5 18:32:52 2016
@@ -198,6 +198,25 @@ namespace std {
       storage.assignExternal(new _CharT[4]);
     }
   };
+
+template<class _Engine, class _UIntType>
+class __independent_bits_engine {
+public:
+  // constructors and seeding functions
+  __independent_bits_engine(_Engine& __e, size_t __w);
+};
+
+template<class _Engine, class _UIntType>
+__independent_bits_engine<_Engine, _UIntType>
+    ::__independent_bits_engine(_Engine& __e, size_t __w)
+{
+  // Fake error trigger.
+  // No warning is expected as we are suppressing warning coming
+  // out of std::basic_string.
+  int z = 0;
+  z = 5/z;
+}
+
 }
 
 void* operator new(std::size_t, const std::nothrow_t&) throw();

Modified: cfe/trunk/test/Analysis/inlining/stl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/inlining/stl.cpp?rev=256886&r1=256885&r2=256886&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/inlining/stl.cpp (original)
+++ cfe/trunk/test/Analysis/inlining/stl.cpp Tue Jan  5 18:32:52 2016
@@ -47,3 +47,8 @@ void testBasicStringSuppression_assign(s
                                        const std::basic_string<char32_t> &v2) {
   v = v2;
 }
+
+class MyEngine;
+void testSupprerssion_independent_bits_engine(MyEngine& e) {
+  std::__independent_bits_engine<MyEngine, unsigned int> x(e, 64); // no-warning
+}