C++"new T [size]"不起作用？

Question

我有一个模板类定义为:

#include <stdio.h>
#include <queue>

using namespace std;

template<class T>
class tbufferpool {
private:
    const int m_initial;
    const int m_size;
    const int m_total;
    T *m_buffer;
    vector<T*> m_queue;

public:
    // constructor
    tbufferpool(int initial, int size) : m_initial(initial), m_size(size), m_total(initial*size) {
        m_buffer = new T[m_total];
        T* next_buffer = m_buffer;
        for (int i = 0; i < initial; ++i, next_buffer += size) {
            m_queue.push_back(next_buffer);
        }
    }

在构造函数中的某些时候我做了:

m_buffer = new T[size];

这适用于大多数用例,但在一次测试中,我得到valgrind报告的以下内存错误(下面的命令和相关代码段)测试仍然正常.有趣的一点是operator new(unsigned long)意味着它不是为我所预期的具体T型I设置"双"分配和对齐但是对于unsigned long？如果我修改我的缓冲池实现和硬编码,new double[size]那么这个内存错误没有显示,但我当然只能使用它tbufferpool<double>.

谁能建议如何解决这个问题？这new T[size]应该合法吗？因为模板参数在编译时由预处理器应用,该预处理器为所使用的每个模板类型创建新类.这会是编译器错误吗？

test_matrix是一个包含30个测试用例的套件.只有一个测试产生下面valgrind中显示的问题,然而测试通过了.我检查了函数调用的所有输入,其中问题源自new T[size]变量,并使用变量将它们与相同的输入一起打印new double[size].我使用AraxisMerge比较它们并且它们是相同的.我担心与内存对齐有关的问题根据我是使用模板参数还是具体的双重类型而变得不同......？

$ valgrind --show-reachable=yes --dsymutil=yes --track-origins=yes ./test_matrix
  [snip]
  ==3719== Conditional jump or move depends on uninitialised value(s)
  ==3719==    at 0x3BE86C8: mkl_blas_dscal (in /opt/intel/composerxe-2011.4.184/mkl/lib/libmkl_mc3.dylib)
  ==3719==    by 0x432FFFFFFFFFFFFF: ???
  ==3719==  Uninitialised value was created by a heap allocation
  ==3719==    at 0xD62F: malloc (vg_replace_malloc.c:266)
  ==3719==    by 0x97B15C: operator new(unsigned long) (in /opt/local/lib/gcc46/libstdc++.6.dylib)
  ==3719==    by 0x7FFF5FBFE54F: ???
  ==3719==    by 0x10014BDBF: ???
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x97B288: operator new[](unsigned long) (in /opt/local/lib/gcc46/libstdc++.6.dylib)
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x100013853: tbufferpool<double>::tbufferpool(int, int) (bufferpool.h:30)
  ==3719==    by 0x7003FFFFF: ???
  ==3719==    by 0x100079E7F: ??? (in ./test_matrix)
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x10014BE0F: ???
  ==3719== 
  ==3719== Conditional jump or move depends on uninitialised value(s)
  ==3719==    at 0x3BE86CA: mkl_blas_dscal (in /opt/intel/composerxe-2011.4.184/mkl/lib/libmkl_mc3.dylib)
  ==3719==    by 0x432FFFFFFFFFFFFF: ???
  ==3719==  Uninitialised value was created by a heap allocation
  ==3719==    at 0xD62F: malloc (vg_replace_malloc.c:266)
  ==3719==    by 0x97B15C: operator new(unsigned long) (in /opt/local/lib/gcc46/libstdc++.6.dylib)
  ==3719==    by 0x7FFF5FBFE54F: ???
  ==3719==    by 0x10014BDBF: ???
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x97B288: operator new[](unsigned long) (in /opt/local/lib/gcc46/libstdc++.6.dylib)
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x100013853: tbufferpool<double>::tbufferpool(int, int) (bufferpool.h:30)
  ==3719==    by 0x7003FFFFF: ???
  ==3719==    by 0x100079E7F: ??? (in ./test_matrix)
  ==3719==    by 0x7FFF5FBFE58F: ???
  ==3719==    by 0x10014BE0F: ???
  [snip]

系统细节:

/Users/bravegag/code/fastcode_project/build_debug$ uname -a && g++ --version
Darwin Macintosh-4.local 11.3.0 Darwin Kernel Version 11.3.0: Thu Jan 12 18:47:41 PST 2012; 
root:xnu-1699.24.23~1/RELEASE_X86_64 x86_64
g++ (GCC) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Answer 1

请注意之间的区别

m_buffer = new T[size];

和

m_buffer = new T[size]();

在前一种情况下，数组未初始化，因此出现 valgrind 错误：

Conditional jump or move depends on uninitialised value

也就是说，根据我的经验，在这种情况下您可以忽略这个特定的 valgrind 输出。由于您显然使用某种 blas 实现，因此很可能它是 BLAS 库内部优化的效果，不会做坏事。