How come this code
std::map <std::string , int> m;
m["a"]=1;
compiles with (I'm using MSVC 2010)
#include <string>
but not with
#include <string.h>
?
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10 Answers
93
<string.h>contains old functions likestrcpy,strlenfor C style null-terminated strings.<string>primarily contains thestd::string,std::wstringand other classes.
Ajay
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38It should also be noted that using `string.h` is deprecated within C++. If you need the functionality contained within, you should use the header `cstring`. This more or less completely bypasses the issue of "What's the difference between these two" because it's very obvious that one is from the C library. – Mike Bailey Mar 11 '12 at 20:53
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string.h is a C header not a C++ header, period!
Prasoon Saurav
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Do you mean that when I do a couple of files .h/.cpp I should remove the .h or is your answer just for euh, like sdk files? – Valmond Feb 13 '12 at 09:05
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18I think, it's better to say the other way: `
is C++ header, not a C header.` – iammilind Feb 13 '12 at 09:06
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<string.h> is cstring - http://www.cplusplus.com/reference/clibrary/cstring/
<string> is the c++ string class - http://www.cplusplus.com/reference/string/
Edit per Nicol Bolas comment below and a bit of googling:
<cstring> will usually import the same things as <string.h> but into the std namespace.
<string.h> will usually import everything into the global namespace.
It appears to depend on the library implementation you're using though according to my googling.
Personally I only ever use <cstring> if I need C style string helpers.
matiu
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2`
` is not a synonym for ` – Nicol Bolas Feb 13 '12 at 08:53`. `cstring` puts stuff in the `std` namespace (it may also leave them outside of the `std` namespace), while ` ` does not. -
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@PrasoonSaurav To be deprecated it would have to have been part of the standard to begin with, which it never was. – Peter Wood Feb 13 '12 at 09:52
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<string.h> contains C-library string functions. strlen, strcmp, etc.
<string> contains the definition for std::basic_string, which has the typedefs std::string and std::wstring. That's the difference.
They really have no relationship at all, outside of the fact that they both deal with strings.
Nicol Bolas
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They are entirely different headers.
<string> is C++ string class
<string.h> or <cstring> defines functions to manipulate C strings and arrays
Sanish Gopalakrishnan
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As stated, string.h and cstring are C headers (while cstring is basically a C++ wrapper for string.h), containing functions for C strings, which are char[] terminated by '\0'. You want to use the c++ class string, which header is <string>.
Zeta
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<string.h> is a C standard library header while <string> is a cpp in fact all the c standard header files have .h extension an non of cpp have .h.
PankajSingh
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