C++ 为什么根据标题的包含顺序会出现分段错误？

我有以下文件，它是一个较大（但仍然很小）程序的一部分。程序编译时不考虑头的包含顺序，但如果在本地文件之后包含

，则会出现seg错误；如果在本地头文件之前包含它，程序运行正常

#include <fstream>
#include "Bitmap.h"
#include "BitmapInfoHeader.h"
#include "BitmapFileHeader.h"

namespace bmap
{

Bitmap::Bitmap(int width, int height) : _width(width), _height(height), _pixels(new uint8_t[width * height * 3]{}) { }

void Bitmap::set_pixel(int x, int y, uint8_t red, uint8_t blue, uint8_t green) { }

bool Bitmap::write(string filename)
{
  BitmapFileHeader file_header;
  BitmapInfoHeader info_header;

  file_header.file_size = sizeof(BitmapInfoHeader) + sizeof(BitmapFileHeader) + _width * _height * 3;
  file_header.data_offset = sizeof(BitmapInfoHeader) + sizeof(BitmapFileHeader);

  info_header.width = _width;
  info_header.height = _height;

  std::ofstream outfile(filename, ios::out | ios::binary);
  if(!outfile) { return false; }
  outfile.write((char *)(&file_header), sizeof(file_header));
  outfile.write((char *)(&info_header), sizeof(info_header));
  outfile.write((char *)(_pixels.get()), _width * _height * 3);
  outfile.close();
  return true;
}

Bitmap::~Bitmap() { }

}

---

这是C++，不是最可能的C++行为。通常，这是代码中未定义行为的标志。您忘记将打包设置为默认值：<代码> RustyX > PrimaPACK（）/Cuth>谢谢大家，尤其是@我不知道我必须将打包打包回默认值。很可能是未定义的行为。通常这是代码中未定义行为的标志。您忘记将打包设置回默认值：

#pragma pack（）

感谢大家，尤其是@RustyX，我不知道我必须将打包设置回默认值。

#ifndef BITMAP_H_
#define BITMAP_H_

#include <cstdint>
#include <string>

using namespace std;

namespace bmap{

class Bitmap
{
 private:
  int _width{0};
  int _height{0};
  unique_ptr<uint8_t[]> _pixels{nullptr};

 public:
  Bitmap(int width, int height);
  bool write(string filename);
  void set_pixel(int x, int y, uint8_t red, uint8_t blue, uint8_t green);
  virtual ~Bitmap();
};
}

#endif

#ifndef BITMAPFILEHEADER_H_
#define BITMAPFILEHEADER_H_

#include <cstdint>

namespace bmap
{

#pragma pack(2)
struct BitmapFileHeader
{
  char header[2]{ 'B', 'M' };
  int32_t file_size;
  int32_t reserved{0};
  int32_t data_offset;
};
}

#endif

#ifndef BITMAPINFOHEADER_H_
#define BITMAPINFOHEADER_H_

#include <cstdint>

namespace bmap
{

#pragma pack(2)
  struct BitmapInfoHeader
  {
    int32_t header_size{40};
    int32_t width;
    int32_t height;
    int16_t planes{1};
    int16_t bits_per_pixel{24};
    int32_t compression{0};
    int32_t data_size{0};
    int32_t horizontal_resolution{2400};
    int32_t vertical_resolution{2400};
    int32_t colors{0};
    int32_t important_colors{0};
  };
}
#endif

Program received signal SIGSEGV, Segmentation fault.
0x00007fff994bdf24 in std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush() () from /usr/lib/libc++.1.dylib
(gdb) where
#0  0x00007fff994bdf24 in std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush() () from /usr/lib/libc++.1.dylib
#1  0x00007fff994c299e in std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::sentry(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) () from /usr/lib/libc++.1.dylib
#2  0x00007fff994c41a6 in std::__1::basic_ostream<char, std::__1::char_traits<char> >::write(char const*, long) () from /usr/lib/libc++.1.dylib
#3  0x0000000100001626 in bmap::Bitmap::write (this=0x7fff5fbffa50, filename=...) at Bitmap.cpp:26
#4  0x0000000100004d48 in main () at Mandelbrot.cpp:11
(gdb)