Avoid memory leak when constructor of user-defined type throws exception.

The added check `ctorleak.cpp` demonstrates how the leak can be reproduced.
The test appears to pass but it is leaking the storage of the (not created)
matrix.  I don't know how to make this test fail in the existing test suite but
you can run it through Valgrind (or another debugger) to verify the leak.

    $ ./check.sh ctorleak && valgrind --leak-check=full ./test/ctorleak

This patch fixes this leak by adding some try-catch-delete-rethrow blocks to
`Eigen/src/Core/util/Memory.h`.

Eigen/src/Core/util/Memory.h

@@ -338,15 +338,6 @@ template<> inline void* conditional_aligned_realloc<false>(void* ptr, size_t new
 *** Construction/destruction of array elements                             ***
 *****************************************************************************/
 
-/** \internal Constructs the elements of an array.
-  * The \a size parameter tells on how many objects to call the constructor of T.
-  */
-template<typename T> inline T* construct_elements_of_array(T *ptr, size_t size)
-{
-  for (size_t i=0; i < size; ++i) ::new (ptr + i) T;
-  return ptr;
-}
-
 /** \internal Destructs the elements of an array.
   * The \a size parameters tells on how many objects to call the destructor of T.
   */
@@ -357,6 +348,24 @@ template<typename T> inline void destruct_elements_of_array(T *ptr, size_t size)
     while(size) ptr[--size].~T();
 }
 
+/** \internal Constructs the elements of an array.
+  * The \a size parameter tells on how many objects to call the constructor of T.
+  */
+template<typename T> inline T* construct_elements_of_array(T *ptr, size_t size)
+{
+  size_t i;
+  try
+    {
+      for (i = 0; i < size; ++i) ::new (ptr + i) T;
+      return ptr;
+    }
+  catch (...)
+    {
+      destruct_elements_of_array(ptr, i);
+      throw;
+    }
+}
+
 /*****************************************************************************
 *** Implementation of aligned new/delete-like functions                    ***
 *****************************************************************************/
@@ -376,14 +385,30 @@ template<typename T> inline T* aligned_new(size_t size)
 {
   check_size_for_overflow<T>(size);
   T *result = reinterpret_cast<T*>(aligned_malloc(sizeof(T)*size));
+  try
+    {
       return construct_elements_of_array(result, size);
+    }
+  catch (...)
+    {
+      aligned_free(result);
+      throw;
+    }
 }
 
 template<typename T, bool Align> inline T* conditional_aligned_new(size_t size)
 {
   check_size_for_overflow<T>(size);
   T *result = reinterpret_cast<T*>(conditional_aligned_malloc<Align>(sizeof(T)*size));
+  try
+    {
       return construct_elements_of_array(result, size);
+    }
+  catch (...)
+    {
+      conditional_aligned_free<Align>(result);
+      throw;
+    }
 }
 
 /** \internal Deletes objects constructed with aligned_new
@@ -412,7 +437,17 @@ template<typename T, bool Align> inline T* conditional_aligned_realloc_new(T* pt
     destruct_elements_of_array(pts+new_size, old_size-new_size);
   T *result = reinterpret_cast<T*>(conditional_aligned_realloc<Align>(reinterpret_cast<void*>(pts), sizeof(T)*new_size, sizeof(T)*old_size));
   if(new_size > old_size)
+    {
+      try
+        {
           construct_elements_of_array(result+old_size, new_size-old_size);
+        }
+      catch (...)
+        {
+          conditional_aligned_free<Align>(result);
+          throw;
+        }
+    }
   return result;
 }
 
@@ -422,7 +457,17 @@ template<typename T, bool Align> inline T* conditional_aligned_new_auto(size_t s
   check_size_for_overflow<T>(size);
   T *result = reinterpret_cast<T*>(conditional_aligned_malloc<Align>(sizeof(T)*size));
   if(NumTraits<T>::RequireInitialization)
+    {
+      try
+        {
           construct_elements_of_array(result, size);
+        }
+      catch (...)
+        {
+          conditional_aligned_free<Align>(result);
+          throw;
+        }
+    }
   return result;
 }
 
@@ -434,7 +479,17 @@ template<typename T, bool Align> inline T* conditional_aligned_realloc_new_auto(
     destruct_elements_of_array(pts+new_size, old_size-new_size);
   T *result = reinterpret_cast<T*>(conditional_aligned_realloc<Align>(reinterpret_cast<void*>(pts), sizeof(T)*new_size, sizeof(T)*old_size));
   if(NumTraits<T>::RequireInitialization && (new_size > old_size))
+    {
+      try
+        {
           construct_elements_of_array(result+old_size, new_size-old_size);
+        }
+      catch (...)
+        {
+          conditional_aligned_free<Align>(result);
+          throw;
+        }
+    }
   return result;
 }
 

test/CMakeLists.txt

@@ -251,6 +251,8 @@ ei_add_test(bicgstab)
 ei_add_test(sparselu)
 ei_add_test(sparseqr)
 
+ei_add_test(ctorleak)
+
 # ei_add_test(denseLM)
 
 if(QT4_FOUND)

test/ctorleak.cpp

@@ -0,0 +1,43 @@
+#include "main.h"
+
+#include <exception>  // std::exception
+
+struct Foo
+{
+  int dummy;
+  Foo() { if (!internal::random(0, 10)) throw Foo::Fail(); }
+  class Fail : public std::exception {};
+};
+
+namespace Eigen
+{
+  template<>
+  struct NumTraits<Foo>
+  {
+    typedef double Real;
+    typedef double NonInteger;
+    typedef double Nested;
+    enum
+      {
+        IsComplex             =  0,
+        IsInteger             =  1,
+        ReadCost              = -1,
+        AddCost               = -1,
+        MulCost               = -1,
+        IsSigned              =  1,
+        RequireInitialization =  1
+      };
+    static inline Real epsilon() { return 1.0; }
+    static inline Real dummy_epsilon() { return 0.0; }
+  };
+}
+
+void test_ctorleak()
+{
+  try
+    {
+      Matrix<Foo, Dynamic, Dynamic> m(14, 92);
+      eigen_assert(false);  // not reached
+    }
+  catch (const Foo::Fail&) { /* ignore */ }
+}