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Full Discussion: How to get the sizeof char pointer
Top Forums Programming How to get the sizeof char pointer Post 302322235 by pludi on Wednesday 3rd of June 2009 07:24:19 AM
Old 06-03-2009
First, please use [code][/code] where applicable
Code:
using namespace std;
static void cstrCopy(char *x, const char *y);
int main()
{
    char x[19];
    const string y = "UNIX FORUM";
    cstrCopy(x, y.c_str());
    return 0;
}
void cstrCopy(char *x, const char *y)
{
    if (strlen(y) >= sizeof(x)) {
        throw errorException;
    }
    strncpy(x, y, sizeof(x));
}

Second, a C "string" has no information about itself. It's just an array of characters, which is terminated by a null byte by convention. This also means that your two calls to sizeof will always return 4 (size of a pointer). Better add another parameter with the size of the array.
A more intelligent solution would be to malloc() the "C string" in your function, strncpy() the contents of y, and return the pointer to that memory area.
 

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LEARN ABOUT DEBIAN

std::type_info

std::type_info(3cxx)													      std::type_info(3cxx)

NAME

       std::type_info -

SYNOPSIS

       Inherited by __cxxabiv1::__array_type_info, __cxxabiv1::__class_type_info, __cxxabiv1::__enum_type_info, __cxxabiv1::__function_type_info,
       __cxxabiv1::__fundamental_type_info, and __cxxabiv1::__pbase_type_info.

   Public Member Functions
       virtual ~type_info ()
       virtual bool __do_catch (const type_info *__thr_type, void **__thr_obj, unsigned __outer) const
       virtual bool __do_upcast (const __cxxabiv1::__class_type_info *__target, void **__obj_ptr) const
       virtual bool __is_function_p () const
       virtual bool __is_pointer_p () const
       bool before (const type_info &__arg) const
       size_t hash_code () const   throw ()
       const char * name () const
       bool operator!= (const type_info &__arg) const
       bool operator== (const type_info &__arg) const

   Protected Member Functions
       type_info (const char *__n)

   Protected Attributes
       const char * __name

Detailed Description
       Part of RTTI.

       The type_info class describes type information generated by an implementation.

       Definition at line 91 of file typeinfo.

Constructor &; Destructor Documentation
   virtual std::type_info::~type_info () [virtual]
       Destructor first. Being the first non-inline virtual function, this controls in which translation unit the vtable is emitted. The compiler
       makes use of that information to know where to emit the runtime-mandated type_info structures in the new-abi.

Member Function Documentation
   const char* std::type_info::name () const [inline]
       Returns an implementation-defined byte string; this is not portable between compilers!

       Definition at line 102 of file typeinfo.

Author
       Generated automatically by Doxygen for libstdc++ from the source code.

libstdc++							  Tue Nov 27 2012					      std::type_info(3cxx)
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