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);
        }
    }

在构造函数中的某个时刻我做了:

m_buffer = new T[size];

这适用于大多数用例，但在一次测试中，我收到 valgrind 报告的以下内存错误(下面的命令和相关代码段)，但测试仍然顺利通过。有趣的一点是 operator new(unsigned long)这意味着它没有为我设置的具体 T 类型分配和对齐，正如我预期的那样，但对于 unsigned long ？如果我修改我的缓冲池实现和硬编码 new double[size]然后这个内存错误没有显示，但当然我只使用 tbufferpool<double>现在。

有人可以建议如何解决这个问题吗？ new T[size]应该合法吧？因为模板参数是在编译时由预处理器应用的，预处理器为每个使用的模板类型创建一个新类。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。只有一个测试在 valgrind 中产生如下所示的问题，但该测试通过了。我使用 new T[size] 检查了问题起源的函数调用的所有输入。变体并使用 new double[size] 将它们与相同的输入一起打印变种。我使用 AraxisMerge 比较它们，它们是相同的。恐怕是与内存对齐相关的问题根据我使用的是模板参数还是具体的 double 类型而有所不同......？

$ 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]

系统详情:

/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.

最佳答案

请注意区别

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。由于您显然使用了某种 blas 实现，很可能这是 BLAS 库内部优化的结果，不会做坏事。

关于C++ "new T[size]"不起作用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10447683/