getchar_unlocked in windows undeclared

Question

Here is my code:

#include 

void scan(int* i)
{
    int t=0;
    char c;
    bool negative=false;
    c=getchar_unlocked();
    while(c<\'0         


        

Answer 1

getchar_unlocked is not a C or C++ standard function and therefore it's no surprise that it doesn't work on Windows. It is a POSIX standard I think, but Windows compilers don't support all POSIX functions.

If you replaced getchar_unlocked with getchar, it would kind of work, although the algorithm doesn't seem quite right.

You could do this with conditional compilation, like this for instance

#ifdef _WINDOWS
// no getchar_unlocked on Windows so just call getchar
inline int getchar_unlocked() { return getchar(); }
#endif

Answer 2

Windows have the equivalent, _getchar_nolock, it is Windows specific.

See this link:

https://msdn.microsoft.com/en-us/library/4y2e9z0c.aspx

So if you are happy with a non-threadsafe version and you want the best possible performance you could do something like this:

#ifdef WIN32
// no getchar_unlocked on Windows so call _getchar_nolock
inline int getchar_unlocked() { return _getchar_nolock(); }
#endif

Answer 3

getchar_unlocked() is mainly used for competitive programming, however, if you want to use this elsewhere, just make sure, only 1 thread is using it at a time. Same applies to putchar_unlocked() function too. It is a POSIX equivalent so Windows compiler doesn't support it. However, you can use either of two-

1) Normal speed

int getchar_unlocked() { return getchar(); }
void putchar_unlocked(char _c) {return putchar(_c); }

2) Fast speed

int getchar_unlocked() { return _getchar_nolock(); }
void putchar_unlocked(char _c) { return _putchar_nolock(_c); }