problem while using strod

**technosavvy** · 03-20-2008

How can i check if there was any overflow or underflow when using strtod..

i googled about it and found that some HUGE_VAL is set accordingly...
but when i used

Code:

double temp = atof(yytext);
	if (temp == HUGE_VAL)

on compilation, i got an error: error C2065: 'HUGE_VAL' : undeclared identifier

i am right now compiling the code on a windows machine, but my code will be finally sun on both windows and linux..

**matsp** · 03-20-2008

First of all, atof() is different in this sense than strtod(). atof() is not guaranteed to catch bad input at all.

The strtod() function specifies that it will detect overflows.

HUGE_VAL is supposed to be defined in <math.h> - do you include that file?

--
Mats

**technosavvy** · 03-20-2008

thanks .... i didn't include math.h initially.. :-|

there is another thing that i need to know...is HUGE_VAL macro part of C89 standards..
if it is not then how can we have a check for huge values while writing a code strictly conforming to C89...

**technosavvy** · 03-20-2008

and i have written atof in my first post by mistake.. i am using strtod only..

**matsp** · 03-20-2008

ISO9899:1999, section 7.12.3:

The macro
HUGE_VAL
expands to a positive double constant expression, not necessarily representable as a
float. The macros
HUGE_VALF
HUGE_VALL
are respectively float and long double analogs of HUGE_VAL

Sorry some of the nice formatting in the spec itself got lost there..

--
Mats

**technosavvy** · 03-20-2008

but is HUGE_VAL part of C89 standard...
if i am not wrong you have quoted using the C99 standard..

bear me if i am wrong :-)

**matsp** · 03-20-2008

Doh! Sorry, the caffeine from the Coke obviously hasn't quite worked it's way in yet.

I'll see if I can find out. FWIW, gcc -ansi -std=c89 -pedantic -Wall compiles this:

Code:

#include <math.h>
#include <stdio.h>

int main() 
{ 
   printf("%f", HUGE_VAL); 
   return 0; 
}

That's using gcc-mingw 3.4.2.
--
Mats

**technosavvy** · 03-20-2008

hehe...
i checked ...HUGE_VAL is there in the C89 draft...

**matsp** · 03-20-2008

Originally Posted by technosavvy

hehe...
i checked ...HUGE_VAL is there in the C89 draft...

Good. And if it's in the draft, then it will be in the ratified version as well, as I can't see why it would be a contentious issue that got removed from the draft.

--
Mats

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