strdup or _strdup?

When I use strdup in Microsoft Visual C++, it warns me:

warning C4996: 'strdup': The POSIX name for this item is deprecated. Instead, use the ISO C++ conformant name: _strdup. See online help for details.

Thus it seems _strdup is correct.

But when I use _strdup in GCC (Fedora Linux OS), the compiler shows an error:

error: ‘_strdup’ was not declared in this scope

With GCC and Linux, compiler does not show any error for strdup开发者_开发知识库.

Which is correct - strdup or _strdup?

Note: I include <string.h> in my code.

---

Which is correct?

strdup is a perfectly correct POSIX function. Nevertheless, it doesn't belong to the standard, and the ANSI C standard reserves some (broad) classes of function names for further use. Among these, there are

• Function names that begin with str and a lowercase letter

therefore, the MS guys decided to replace strdup with _strdup.

I'd just continue using strdup. It's unlikely the C committee will define strdup to something else than POSIX. Either #define strdup _strdup or silence the warning.

BTW I hope you see this applies to your functions with names like string_list etc., too.

---

strdup is not a standard C++ function. but it is apparently a Posix function, and anyway it's a well known function which has been there since K&R C. so if you absolutely must use it, do not fret about any possible name collision, and just write strdup for maximum portability.

---

You can #define _CRT_NONSTDC_NO_DEPRECATE to disable this warning.

---

If you just want to avoid the Warning message:

Project-> property -> C/C++ -> Preprocessor -> Preprocessor Definitions

Edit this, and add

_CRT_NONSTDC_NO_DEPRECATE

---

strdup is POSIX:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/strdup.html

_strdup is Windows specific:

http://msdn.microsoft.com/en-us/library/y471khhc(v=vs.80).aspx

On Unix, use strdup. On Windows, use _strdup. It's that simple. If you need to write portable code between Unix and Windows:

• use system dependent macros (for example _WIN32 vs. _POSIX_VERSION) to select the proper function (but notice that the macros may depend on specific pre existing include files):

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/unistd.h.html

http://msdn.microsoft.com/en-us/library/b0084kay(v=vs.80).aspx

• use standard functions to reimplement strdup: strlen, malloc and memmove.

• use a cross platform utility library, like glib:

http://developer.gnome.org/glib/2.28/glib-String-Utility-Functions.html#g-strdup

Note that Visual C++ message suggests that _strdup belongs to the C++ standard, but this is false, as it can be verified on the C++ standard. It merely uses the underscore prefix as a "namespace" for the function.

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3376.pdf

---

Don't know about C++.

The C Standard does not describe any function with the strdup name (though the name is reserved). To be portable, in C, you're better off replacing that with malloc, strcpy, and free.

---

it's not a warning but an error reported in higher version of vs.

use macro #ifdef WIN32 to switch