Re: \0 in std::string

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Fri, 16 Mar 2007 10:03:14 -0400

Message-ID:

<ete838$fst$1@news.datemas.de>

Stefan Naewe wrote:

On 3/16/2007 2:10 PM, Victor Bazarov wrote:

Stefan Naewe wrote:

A simple test:

<---------------------------->
#include <string>
#include <iostream>

int main()
{
   std::string h("Hello ");
   *h.rbegin() = '\0';
   std::string w=h+std::string(" World");

   std::cout << w << std::endl;
   return 0;
}
<---------------------------->

Output with different compilers:

MSVC6 :
"Hello 12"

gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21):
"Hello World 12"

I know MSVC6 is severely borken but is it correct anyway ?

The resulting string (before output) should be (without the quotes
of course):

"Hello\0 World"

Now, what you see when you output it has been converted into the
output medium representation. I just tested it with VC++ v8, and
got two spaces between the words, which suggests that the null
character is replaced with a space in *my* output.

In order to verify the contents of the string, you need to print it
out char by char.

Which I have done already...and the gcc version indeed outputs the
'\0'.

The problem is that MSVC6's operator<<() for std::basic_string<>
more or less does

stream << str.c_str();

How do you know that? What if it's the 'cout's problem and not the
operator's? The operator stuffs the characters into the buffer. What
the buffer does with those characters is implementation-defined, AFAIK.

which in turn uses strlen(s) the get the length of the sequence to be
output. So, another stupidity in our beloved compiler...

Uh... Wait a minute. But by extension, gcc is also wrong. What's that
"12" at the end of each of them? Is that how your system displays the
'\n'? Who's to say how your system reacts to the \0 in the output
stream?

V
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