Re: pragma pack(1) on struct contains object

In our project, one used the following struct

#pragma pack(1)
struct Foo {
  uint8_t b1;
  uint8_t b2;
  uint8_t b3;
  std::vector<uint8_t> buf;
  ...
};
#pragma pack()

this work on PC, but not on ARM target using a gcc/g++ cross
compiler. The problem is, on ARM, after defined a variable of Foo
and want to access a method of buf, such as

    Foo foo;
    foo.buf.resize(100);

the program will exit. I guss it's a segment failure.

Can you experts explain for me the reason?

I know, it is suspious that why this guy use pack(1) on this kind of
struct, but we can just ignore it and focus on the underlying reason why
the usage cause the failure.