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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::messages_byname

std::messages_byname< _CharT >(3cxx)									      std::messages_byname< _CharT >(3cxx)

NAME

       std::messages_byname< _CharT > -

SYNOPSIS

       Inherits std::messages< _CharT >.

   Public Types
       typedef int catalog
       typedef _CharT char_type
       typedef basic_string< _CharT > string_type

   Public Member Functions
       messages_byname (const char *__s, size_t __refs=0)
       void close (catalog __c) const
       string_type get (catalog __c, int __set, int __msgid, const string_type &__s) const
       catalog open (const basic_string< char > &__s, const locale &__loc) const
       catalog open (const basic_string< char > &, const locale &, const char *) const

   Static Public Attributes
       static locale::id id

   Protected Member Functions
       string_type _M_convert_from_char (char *) const
       char * _M_convert_to_char (const string_type &__msg) const
       virtual void do_close (catalog) const
       virtual string_type do_get (catalog, int, int, const string_type &__dfault) const
       template<> string do_get (catalog, int, int, const string &) const
       template<> wstring do_get (catalog, int, int, const wstring &) const
       virtual catalog do_open (const basic_string< char > &, const locale &) const

   Static Protected Member Functions
       static __c_locale _S_clone_c_locale (__c_locale &__cloc)  throw ()
       static void _S_create_c_locale (__c_locale &__cloc, const char *__s, __c_locale __old=0)
       static void _S_destroy_c_locale (__c_locale &__cloc)
       static __c_locale _S_get_c_locale ()
       static const char * _S_get_c_name ()  throw ()
       static __c_locale _S_lc_ctype_c_locale (__c_locale __cloc, const char *__s)

   Protected Attributes
       __c_locale _M_c_locale_messages
       const char * _M_name_messages

Detailed Description
   template<typename _CharT>class std::messages_byname< _CharT >
       class messages_byname [22.2.7.2].

       Definition at line 1912 of file locale_facets_nonio.h.

Member Data Documentation
   template<typename _CharT > locale::id std::messages< _CharT >::id [static],	[inherited]
       Numpunct facet id.

       Definition at line 1713 of file locale_facets_nonio.h.

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

libstdc++							  Tue Nov 27 2012			      std::messages_byname< _CharT >(3cxx)
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