Weird behavior writing/reading simple binary file - c++

Question

I'm writing and reading on a binary file. I'm getting small errors when outputting the reads.
The strings are there but with little snippets like: (I"�U) (�U) appended to the end of ~30% of them
I'm using g++ compiler on Ubuntu
Simplified code:
struct Db_connection
{
public:
string name;
}
int Db_connection::write_config()
{
ofstream config_f("config.dat", std::ios_base::binary | std::ios_base::out); //open file
string str = name;
int size = str.length();
config_f.write(reinterpret_cast<char *>(&size), sizeof(int)); // write size of string in int size chunk
config_f.write(str.c_str(), size); //write string
config_f.close();
return 0;
}
Db_connection read_config()
{
ifstream config_f("config.dat", std::ios_base::binary | std::ios_base::in);
Db_connection return_obj;
int size;
string data;
config_f.read(reinterpret_cast<char *>(&size), sizeof(int)); // read string size
char buffer[size];
config_f.read(buffer, size); // read string
data.assign(buffer);
return_obj.name = data;
return return_obj;
}
Is there anything obvious I am messing up? Does this have to do with Endian? I tried to minimize the code to it's absolute essentials
The actual code is more complex. I have a class holding vectors of 2 structs. 1 struct has four string members and the other has a string and bool. These fuctions are actually a member of and return (respectively) that class. The fuctions loop through the vectors writing struct members sequentially.
Two oddities:
To debug, I added outputs of the size and data variables on each iteration in both the read and write functions. size comes out accurate and consistent on both sides. data is accurate on the write side but with the weird special characters on the read side. I'm looking at outputs like:
Read Size: 12
Data: random addy2�U //the 12 human readable chars are there but with 2 extra symbols
The final chunk of data (a bool) comes out fine every time, so I don't think there is a file pointer issue. If its relevant: every bool and int is fine. Its just a portion of the strings.
Hopefully i'm making a bonehead mistake and this minimized code can be critiqued. The actual example would be too long.

Answer 1

Big thanks to WhozCraig,
The following edit did, indeed, work:
Db_connection read_config()
{
ifstream config_f("config.dat", std::ios_base::binary | std::ios_base::in);
Db_connection return_obj;
int size;
string data;
config_f.read(reinterpret_cast<char *>(&size), sizeof(int)); // read string size
vector<char> buff(size);
config_f.read(buff.data(), size);
data = string(buff.begin(), buff.end());
return_obj.name = data;
return return_obj;
}
As paddy pointed out directly and WhozCraig alluded to, this code still needs to implement a standardized, portable data type for recording the integer properly into binary and the write function needs to be rethought as well.
Thank you very much to the both of you. I read like 5-8 top search results for "cpp binary i/o" before writing my code and still ended up with that mess. You guys saved me hours/days of my life.