sizeof string?

This is a discussion on sizeof string? within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> #include <string> using namespace std; int main() { std::string s1 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; std::string s2 = "a"; cout ...

  1. #1
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    sizeof string?

    Code:
    #include <iostream>
    #include <string>
    using namespace std;
    
    int main() {
    	std::string s1 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
    	std::string s2 = "a";
    	cout << sizeof(s1) << endl;
    	cout << sizeof(s2) << endl;
    	cin.get();
    }
    Why does sizeof give me 32 for both strings?

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Why shouldn't it? sizeof is not .size(), after all.

  3. #3
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    >Why does sizeof give me 32 for both strings?
    What you're looking for is s1.length() or s1.size(). sizeof gives you the sizeof the data structure, in this case the size of the string class. For example (sizeof int) would tell you how many bytes an int is on your system. Or cout << std::numeric_limits<int>::max() would print the maximum value an int can contain.

  4. #4
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    strlen()

  5. #5
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    strlen()
    No. strlen() is for C-strings (char *, not std::string).

  6. #6
    and the hat of sweating
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    I actually saw some developers at a previous job use:
    Code:
    strlen( something.c_str() );
    Luckily I was on the other side of the building when I was reviewing the code, so they couldn't hear me laughing my ass off.

  7. #7
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    Quote Originally Posted by cpjust View Post
    I actually saw some developers at a previous job use:
    Code:
    strlen( something.c_str() );
    Luckily I was on the other side of the building when I was reviewing the code, so they couldn't hear me laughing my ass off.
    Looks like they learned C++ using Visual Studio 7 or something. If I recall correctly there was a time when M$ compilers didn't implement the string class completely

  8. #8
    The larch
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    Such a lack in the implementation could be hard to believe, though

    Anyway, here's my homemade string class. It is a lot safer than std::string, but it misses a few features that would make it complete:

    Code:
    class String
    {
        public:
        unsigned capacity() const { return 0; }
        bool empty() const { return true; }
        unsigned find( const String& str, unsigned index ) const { return std::numeric_limits<unsigned>::max(); }
        unsigned size() const { return 0; }
        //TO_DO: add other methods
    };
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  9. #9
    and the hat of sweating
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    Quote Originally Posted by pantherse View Post
    Looks like they learned C++ using Visual Studio 7 or something. If I recall correctly there was a time when M$ compilers didn't implement the string class completely
    Well the std::string in VC++ 6.0 seems fairly correct. I haven't used anything earlier than that.

    Quote Originally Posted by anon View Post
    Such a lack in the implementation could be hard to believe, though

    Anyway, here's my homemade string class. It is a lot safer than std::string, but it misses a few features that would make it complete:

    Code:
    class String
    {
        public:
        unsigned capacity() const { return 0; }
        bool empty() const { return true; }
        unsigned find( const String& str, unsigned index ) const { return std::numeric_limits<unsigned>::max(); }
        unsigned size() const { return 0; }
        //TO_DO: add other methods
    };
    LOL!

  10. #10
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    Anyway, here's my homemade string class. It is a lot safer than std::string, but it misses a few features that would make it complete
    I thought the std::string is pretty safe?...

  11. #11
    The larch
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    There are some problems because it has to interface with C-style strings. E.g

    Code:
    std::string s(0);
    I'm not sure if this is required to throw an exception.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  12. #12
    C++ Witch laserlight's Avatar
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    I'm not sure if this is required to throw an exception.
    It is not allowed by the pre-condition, but the behaviour is undefined.
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