[MinGW-notify] [ mingw-Bugs-3536816 ] Seg fault on mingw / gcc 4.7 with csqrt function

[SF/projects/mingw n. l. <min...@li...>]

Bugs item #3536816, was opened at 2012-06-21 01:04
Message generated for change (Comment added) made by clemensx
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=102435&aid=3536816&group_id=2435

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: MinGW
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: clemens (clemensx)
Assigned to: Nobody/Anonymous (nobody)
Summary: Seg fault on mingw / gcc 4.7 with csqrt function

Initial Comment:
Dear all,
I'm running a WinXP 32 bit system on an intel dual core CPU. As a compiler, I'm using the latest gcc version installed by the "mingw-get-inst-20120426.exe". I've only installed the C and C++ cumpiler and used the option "Download the latest...". The following code produces a seg fault which I was able to track down to the csqrt function. Debugging it, it gave me no hint at all what the problem is about.
I'm also running a gcc 4.6.3 build on two different Ubuntu versions, which works fine. It also _worked_ fine when I was using the prior mingw build of gcc 4.6.2. Here's the code:

**********************************************

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

#ifndef complex
	#define complex _Complex
#endif

typedef double complex cdoub;

cdoub ccangl_out(const cdoub ni, const cdoub nt, const double cangl_i, char *tir)
{
double t2=1.-cangl_i*cangl_i;
cdoub t1=1.-ni*ni/(nt*nt)*t2;
if(creal(t1)>0.)
{
	*tir=0;
	return csqrt(t1);
}
else if(creal(t1)==0.)
{
	*tir=1;
	return csqrt(t1);
}
else
{
	*tir=1;
	return -1.*csqrt(t1);
}
}

void testing(void)
{
cdoub no=1.,ni=1.39+(1.1e-7*1.i),c_out;
double c_in;
char tir;

for(c_in=.1;c_in<1.;c_in+=.01)
	c_out=ccangl_out(ni,no,c_in,&tir);

printf("c_out: %g + %gi\n",creal(c_out),cimag(c_out));
}

int main(void)
{
testing();

return 1;
}

**********************************************

Kind regards
Clemens

----------------------------------------------------------------------

>Comment By: clemens (clemensx)
Date: 2012-06-22 09:15

Message:
Hey, here is a simplified one:

**********************************************

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

double complex csqrt_out(const double complex ni)
{
return csqrt(ni);
}

int main(void)
{
double complex ni=1.+1.1e-7*1.i,c_out;

c_out=csqrt(ni);
printf("c_out: %g + %gi\n",creal(c_out),cimag(c_out));

c_out=csqrt_out(ni);
printf("c_out: %g + %gi\n",creal(c_out),cimag(c_out));

return 1;
}

**********************************************

Now, I get the output:

c_out: 1.88963e+265 + 6.72985e+268i

Process returned -1073741819 (0xC0000005)

Which means, that only the second call produces a seg fault, but the first
one a false result. It should read 1. + 5.5*10^-8 I

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=102435&aid=3536816&group_id=2435