What's the difference between strtok_r and strtok_s in C?

Question

I\'m trying to use this function in a C program that needs to be able to compile in Linux and Windows. At first I tried using strtok_r, but then when I compiled on windows,

Answer 1

I don't have enough reputation to comment on other answers, so I'll have to provide my own.

1) To address this statement:

"strtok_s is a buffer overrun safe version of strtok on Windows. The standard strtok on windows is thread safe..."

This is not true. strtok_s is the thread safe version for the MSVC compiler. strtok is not thread safe!

2) To address this statement:

"This would probably break if compiling on Cygwin which reports itself as windows but has POSIX interfaces like strtok_r already defined."

Again, not true. The difference is which compiler you use. When using Microsoft's Visual C++ compiler, MSVC, the function is strtok_s. Another compiler, such as the GNU Compiler Collection, GCC, may use a different standard library implementation such as strtok_r. Think compiler, not target platform, when identifying which function to use.

In my opinion, Joachim Pileborg's answer is the best one on this page. However, it needs a small edit:

#if defined(_WIN32) /* || defined(_WIN64) */
#define strtok_r strtok_s
#endif

Both _WIN32 and _WIN64 are predefined macros provided by the MSVC compiler. _WIN64 is defined when compiling a 64 bit target. _WIN32 is defined for both 32 and 64 bit targets. This is a compromise that Microsoft made for backwards compatibility. _WIN32 was created to specify the Win32 API. Now you should consider _WIN32 to specify Windows API -- it is not specific to a 32 bit target.