using float with CW3

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using float with CW3

NXP Employee
NXP Employee

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Posted: Thu Jun 16, 2005  9:49 am




I do this in a function


float toto;



When i debug it toto is always 2!!!


I don't understand why. I have no error at the compilation.


Thank you very much for help



Posted: Thu Jun 16, 2005  9:56 am


You must put "F" in the end.





Posted: Thu Jun 16, 2005  2:28 pm


I just added this global:

float GLOB=2.14;


(gdb) p GLOB

$1 = 2.1400001


So as per C standard, you do not need 'F' at the end. The '.' indicates float. I guess it must have been something with P&E debugger. I guess my gdb uses more information from debug information to know the variable is a float.



Posted: Thu Jun 16, 2005  5:02 pm


For the ANSI-C standard, you do need the F, otherwise its a double, not a float.


For your case of just initializing a variable, the difference is optimized away as the compiler will do the conversion at compile time. However if you start to use 2.14 as part of a computation and you configured the compiler to support IEEE64 doubles, then you will get a more code when using 2.14 than with 2.14F.



Posted: Thu Jun 16, 2005  9:59 am


It doesn't work :smileysad:



Posted: Thu Jun 16, 2005  10:15 am


Perhaps this is the debugger?


I use P&E product. Is there is something to do for float operations?



Posted: Thu Jun 16, 2005  11:58 am


Ok I find the solution.

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