| # Check whether InterlockedExchange() takes a LONG or a volatile LONG |
| # as its first argument. InterlockedCompareExchange is a windows |
| # function; obviously, this macro is useful only for cygwin and mingw, |
| # and other systems that compile against the windows API. |
| # |
| # Apparently the interface for this function is a bit inconsistent. |
| # Windows likes volatile LONG, but mingw and cygwin don't, at least |
| # for the versions I'm using. But rather than try to guess who |
| # supports what, let's just check at configure time. (Note: this |
| # is an error in C++ but only a warning in C, so we test in the former.) |
| # |
| # This function returns 'yes' if the type does not need volatile, |
| # and defines the symbol INTERLOCKED_EXCHANGE_NONVOLATILE. (This |
| # is the expected case for mingw and cygwin). It returns 'no', |
| # and defines no symbol, otherwise. (This is the expected case for |
| # MSVC.) The return value was sset this way so that we don't need |
| # to define any symbols on windows, which doesn't run configure. |
| |
| AC_DEFUN([AC_INTERLOCKED_EXCHANGE_NONVOLATILE], |
| [ |
| AC_MSG_CHECKING(whether first argument to InterlockedExchange omits volatile) |
| AC_CACHE_VAL(ac_cv_interlocked_exchange_nonvolatile, |
| [AC_LANG_SAVE |
| AC_LANG_CPLUSPLUS |
| AC_TRY_COMPILE([#include <windows.h>], |
| [volatile LONG once; InterlockedExchange(&once, 1);], |
| ac_cv_interlocked_exchange_nonvolatile="no", |
| ac_cv_interlocked_exchange_nonvolatile="yes") |
| AC_LANG_RESTORE |
| ]) |
| if test "$ac_cv_interlocked_exchange_nonvolatile" = "yes"; then |
| AC_DEFINE(INTERLOCKED_EXCHANGE_NONVOLATILE, 1, |
| [define if first argument to InterlockedExchange is just LONG]) |
| fi |
| AC_MSG_RESULT($ac_cv_interlocked_exchange_nonvolatile) |
| ]) |