c++ - assigning values to structure of a class using class object -

i have got strange problem. here code: header file

namespace test { class loadconfigdata {      struct control_params     {          char               active[];          char               suspended[];          char               erased[];             }*ctrl_params; bool loadconfig(); }; }; 

main.cpp

using namespace std; using namespace test; namespace test { extern loadconfigdata           *loadconfigdataobj; loadconfigdata *loadconfigdataobj   = new loadconfigdata; }; int main() { loadconfigdataobj->loadconfig(); cout <<loadconfigdataobj->ctrl_params->active_status_code_v<<endl; cout <<loadconfigdataobj->ctrl_params->suspended_status_code_v<<endl; cout <<loadconfigdataobj->ctrl_params->erase_status_code_v<<endl; return 0; }  bool loadconfigdata::loadconfig() { std::string = "ac"; std::string b = "sp"; std::string c = "er"; loadconfigdata::ctrl_params = new loadconfigdata::control_params; sprintf(loadconfigdataobj->ctrl_params->active,"%s",a.c_str()); sprintf(loadconfigdataobj->ctrl_params->suspended,"%s",b.c_str()); sprintf(loadconfigdataobj->ctrl_params->erased,"%s",c.c_str()); return true; } 

output:

er er er 

which means it's printing last copied string each struct member. wrong in code.

the problem don't give character arrays size:

struct control_params {      char               active[];      char               suspended[];      char               erased[];         }*ctrl_params; 

i'm rather surprised compiles; understanding unsized array incomplete type, , couldn't non-static class member. however, compiler @ least (and presumably yours) treats these arrays of size zero, @ same location in memory. therefore, each time write 1 overwrites whatever wrote others. (of course, behaviour undefined since writes outside array bounds).

the simplest solution use std::string represent strings. manage size automatically, , can write active = a rather messing around sprintf (or, more sensibly, strncpy) , hoping don't buffer overrun.