Re: Another testsuite patch and a bug in string.find

[Benjamin Kosnik <bkoz at cygnus dot com>]

Nathan, did you get a chance to review this? If this is indeed a bug, or a
change in this behavior is necessary, then perhaps string should be fixed?

Also, please use diff -cp. (The relevant parts of the documenation have
been changed to plead for this instead of -up)

-benjamin

On Wed, 7 Jun 2000, Anthony Williams wrote:

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> Here is a patch to testsuite/21_strings/find.cc, which I think makes
> it more standard compliant.
> 
> The patch relates to empty strings. An empty string object contains
> no characters, so I believe that it should be found at all positions,
> and the following code should produce the given output. This
> highlights a bug in string.find, since libstdc++ produces the second
> set of output.
> 
> include <iostream>
> #include <string>
>  
> int main()
> {
>     std::string a("hello");
>     std::string b;
>  
>     for(unsigned i=0;i<=a.size();++i)
>         std::cout<<a.find(b,i)<<std::endl;
> }
>  
> Expected output:
> 0
> 1
> 2
> 3
> 4
> 4294967295
>  
> libstdc++-v3 output:
> 5
> 5
> 5
> 5
> 5
> 5
> 
> Anthony
> 
> testsuite/21_strings/find.cc: Empty strings can be found at all
> positions
> 
> Index: find.cc
> ===================================================================
> RCS file: /cvs/gcc/egcs/libstdc++-v3/testsuite/21_strings/find.cc,v
> retrieving revision 1.1
> diff -u -p -r1.1 find.cc
> - --- find.cc     2000/04/21 20:33:33     1.1
> +++ find.cc     2000/06/07 10:36:09
> @@ -56,21 +56,22 @@ bool test01(void)
>    test &= csz01 == 8;
>    csz01 = str01.find(str03, 12);
>    test &= csz01 == npos;
> - -  // It is implementation-defined if a given string contains an
> empty
> - -  // string. The only two times a char_type() (== empty string)
> ending
> - -  // element is required to be part of the string is on c_str() and
> - -  // operator[size()] const: the indeterminate, stored state of the
> - -  // string can vary, and not include a terminal char_type().
> +
> +  // An empty string consists of no characters
> +  // therefore it should be found at every point in a string,
> +  // except beyond the end
>    csz01 = str01.find(str04, 0);
> - -  test &= csz01 == npos || csz01 == str01.size();
> +  test &= csz01 == 0; 
>    csz01 = str01.find(str04, 5);
> - -  test &= csz01 == npos || csz01 == str01.size();
> +  test &= csz01 == 5; 
> +  csz01 = str01.find(str04, str01.size());
> +  test &= csz01 == npos; 
>    
>    // size_type find(const char* s, size_type pos, size_type n)
> const;
>    csz01 = str01.find(str_lit01, 0, 3);
>    test &= csz01 == 0;
>    csz01 = str01.find(str_lit01, 3, 0);
> - -  test &= csz01 == npos;
> +  test &= csz01 == 3; // zero length string should be found at pos
>  
>    // size_type find(const char* s, size_type pos = 0) const;
>    csz01 = str01.find(str_lit01);
> @@ -107,15 +108,15 @@ bool test01(void)
>    csz01 = str01.find_first_of(str05, 4);
>    test &= csz01 == 4;
>  
> - -  // It is implementation-defined if a given string contains an
> empty
> - -  // string. The only two times a char_type() (== empty string)
> ending
> - -  // element is required to be part of the string is on c_str() and
> - -  // operator[size()] const: the indeterminate, stored state of the
> - -  // string can vary, and not include a terminal char_type().
> +  // An empty string consists of no characters
> +  // therefore it should be found at every point in a string,
> +  // except beyond the end
> +  // However, str1.find_first_of(str2,pos) finds the first character
> in 
> +  // str1 (starting at pos) that exists in str2, which is none for
> empty str2
>    csz01 = str01.find_first_of(str04, 0);
> - -  test &= csz01 == npos || csz01 == str01.size();
> +  test &= csz01 == npos; 
>    csz01 = str01.find_first_of(str04, 5);
> - -  test &= csz01 == npos || csz01 == str01.size();
> +  test &= csz01 == npos; 
>    
>    // size_type find_first_of(const char* s, size_type pos, size_type
> n) const;
>    csz01 = str01.find_first_of(str_lit01, 0, 3);
> 
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