Compiler Warning (level 1) C4293
Collapse the table of content
Expand the table of content
Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here. ArchiveDisclaimer

Compiler Warning (level 1) C4293

Error Message

'operator' : shift count negative or too big, undefined behavior

If a shift count is negative or too large, the behavior of the resulting image is undefined.


The following sample generates C4293:

// C4293.cpp
// compile with: /c /W1
unsigned __int64 combine (unsigned lo, unsigned hi) {

   return (hi << 32) | lo;   // C4293

   // try the following line instead
   // return ( (unsigned __int64)hi << 32) | lo;
© 2015 Microsoft