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use of control87 and floating point underflow

In my c program if I put in the line
_control87(0, EM_ZERODIVIDE |_EM_UNDERFLOW);
I get a floating point underflow exception while running.

However if I change it to
_control87(EM_ZERODIVIDE |_EM_UNDERFLOW, EM_ZERODIVIDE |_EM_UNDERFLOW);
it runs fine.

Please help me undertsand whats wrong here and the correct use of
control87 function.

Aug 23 '06 #1
2 4504
In article <11*********************@i3g2000cwc.googlegroups.c om>,
<jo*****@hotmail.comwrote:
>In my c program if I put in the line
_control87(0, EM_ZERODIVIDE |_EM_UNDERFLOW);
I get a floating point underflow exception while running.
>However if I change it to
_control87(EM_ZERODIVIDE |_EM_UNDERFLOW, EM_ZERODIVIDE |_EM_UNDERFLOW);
it runs fine.
>Please help me undertsand whats wrong here and the correct use of
control87 function.
control87() and _control87() are not part of the C standard. Please
consult a newsgroup more specific to the operating system in question.

My speculation, based upon the 87, is that you are doing something
specific to controlling floating point on the Intel floating point
units (80x87's).

--
"law -- it's a commodity"
-- Andrew Ryan (The Globe and Mail, 2005/11/26)
Aug 23 '06 #2
jo*****@hotmail.com a écrit :
In my c program if I put in the line
_control87(0, EM_ZERODIVIDE |_EM_UNDERFLOW);
I get a floating point underflow exception while running.

However if I change it to
_control87(EM_ZERODIVIDE |_EM_UNDERFLOW, EM_ZERODIVIDE |_EM_UNDERFLOW);
it runs fine.

Please help me undertsand whats wrong here and the correct use of
control87 function.
In cases like this it would be a good idea to READ THE DOCS to
understand what are you doing.

http://msdn2.microsoft.com/en-us/library/e9b52ceh.aspx

Aug 23 '06 #3

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