std :: string如何使用-fwhole程序在GCC中分配内存？ [英] How does std::string allocate memory in GCC with -fwhole-program?

问题描述

更新：以下问题似乎取决于 -fwhole-program 选项。

我一直在玩内存分配，我遇到了一个小谜：在GCC（4.6）， std :: string 如何分配它当我使用 -fwhole-program [/]编译时

$ b >有以下测试程序：

  #include< new> 
 #include< string> 
 #include< iostream> 
 #include< cstdlib> 
 
 void * operator new（std :: size_t n）throw（std :: bad_alloc）
 {
 void * const p = std :: malloc 
 
 if（p == NULL）throw std :: bad_alloc（）; 
 
 std :: cerr<< new（）requests< n<< 字节，分配在< p < .\\\
; 
 
 return p; 
} 
 
 void operator delete（void * p）noexcept 
 {
 std :: cerr< delete（）at<< p < .\\\
; 
 std :: free（p）; 
} 
 
 int main（）
 {
 std :: string s =Hello world。当我使用任何其他动态容器（它使用 
）
 
  ），分配器使用 :: operator new ，所以我很高兴地看到调试消息。但是，使用 std :: string ，我看不到任何东西。我确定动态分配发生，虽然，我可以确认与valgrind（13加上字符串长度字节分配）。我经历了几个源文件和标准，我很确定模板是 std :: basic_string< T，std :: char_traits< T>，std :: allocator< T& ，所以我很失望为什么我没有看到替换的分配函数中的消息。
 
 
 
任何人都可以这个难题？我该如何跟踪字符串分配？此外，任何人都可以通过一些其他编译器运行它，看看它是否产生任何输出？
 
 
 
（例如：如果我添加 std :: map< ; int，int> m {{0，1}};  new（）请求24字节，分配在0x8d53028  ）
解决方案
查看 g ++ ... -S 有/没有 -fwhole-program 看来，使用 fwhole-program 。 
 
 
 
我开始怀疑我们在这里看到一个错误。
 
Update: The following problem appears to depend on the -fwhole-program option.

I've been playing around a bit with memory allocation, and I encountered a small mystery: In GCC (4.6), how does std::string allocate its memory [edit]when I compile with -fwhole-program[/]?

Have this following test program:
#include <new>
#include <string>
#include <iostream>
#include <cstdlib>

void * operator new(std::size_t n) throw(std::bad_alloc)
{
  void * const p = std::malloc(n);

  if (p == NULL) throw std::bad_alloc();

  std::cerr << "new() requests " << n << " bytes, allocated at " << p << ".\n";

  return p;
}

void operator delete(void * p) noexcept
{
  std::cerr << "delete() at " << p << ".\n";
  std::free(p);
}

int main()
{
  std::string s = "Hello world.";
}
When I use any other dynamic container (which uses std::allocator<T>), the allocator uses ::operator new, and so I see the debug messages happily. However, with std::string, I see nothing at all. I'm sure that dynamic allocation happens, though, as I can confirm with valgrind (13 plus string length bytes are allocated). I went through several source files and the standard, and I'm pretty sure that the template is std::basic_string<T, std::char_traits<T>, std::allocator<T>>, so I'm at a loss why I don't see the messages from my replaced allocation functions.

Can anyone shed any light on this conundrum? What do I do to track string allocations? Also, could anyone run this through some other compiler and see if it produces any output?

(For example: if I add std::map<int, int> m { { 0, 1 } };, I have output new() requests 24 bytes, allocated at 0x8d53028 etc.)
解决方案
Looking at the output of g++ ... -S with / without -fwhole-program it appears that the whole custom new/delete operators aren't emitted at all when using fwhole-program. 

I'm starting to suspect we're looking at a bug here.

                        
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