Re: [musl] [BUG] catanf: overflow when the parameter is valid

[Rich Felker <dalias@libc.org>]

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On Wed, Feb 05, 2020 at 08:32:26AM -0500, Rich Felker wrote:
> On Wed, Feb 05, 2020 at 04:33:43PM +0800, sysysongyue@gmail.com wrote:
> >    Hi!
> >    I wrote some testcases for catanf(), and found that catanf(1+0*I) return
> >    99999996802856924650656260769173209088+99999996802856924650656260769173209088*I,
> >    which should return pi/4 in expected. catanl, catanhf, and catanhl have
> >    the same problem. Is this a bug? Any patches existed?
> >    Thank you in advance!
> 
> Looks like the equivalent of commit
> 10e4bd3780050e75b72aac5d85c31816419bb17d for catan was not applied to
> catanf. It should be an easy fix. I'll look at it.
> 
> BTW your mail contained an empty plaintext part and the actual message
> was buried in the html version. I was able to dig it out to reply, but
> try to send text-only or at least with a matching text part since many
> readers probably can't see your email and the archive probably missed
> the body.

Proposed patch attached. It should be identical to the changes in
10e4bd3780050e75b72aac5d85c31816419bb17d except that it's applied to
catanf and catanl.

Rich

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diff --git a/src/complex/catanf.c b/src/complex/catanf.c
index e10d9c09..ef3907a5 100644
--- a/src/complex/catanf.c
+++ b/src/complex/catanf.c
@@ -87,29 +87,17 @@ float complex catanf(float complex z)
 	x = crealf(z);
 	y = cimagf(z);
 
-	if ((x == 0.0f) && (y > 1.0f))
-		goto ovrf;
-
 	x2 = x * x;
 	a = 1.0f - x2 - (y * y);
-	if (a == 0.0f)
-		goto ovrf;
 
 	t = 0.5f * atan2f(2.0f * x, a);
 	w = _redupif(t);
 
 	t = y - 1.0f;
 	a = x2 + (t * t);
-	if (a == 0.0f)
-		goto ovrf;
 
 	t = y + 1.0f;
 	a = (x2 + (t * t))/a;
-	w = w + (0.25f * logf (a)) * I;
-	return w;
-
-ovrf:
-	// FIXME
-	w = MAXNUMF + MAXNUMF * I;
+	w = CMPLXF(w, 0.25f * logf(a));
 	return w;
 }
diff --git a/src/complex/catanl.c b/src/complex/catanl.c
index a9fc02db..e62526c0 100644
--- a/src/complex/catanl.c
+++ b/src/complex/catanl.c
@@ -97,30 +97,18 @@ long double complex catanl(long double complex z)
 	x = creall(z);
 	y = cimagl(z);
 
-	if ((x == 0.0L) && (y > 1.0L))
-		goto ovrf;
-
 	x2 = x * x;
 	a = 1.0L - x2 - (y * y);
-	if (a == 0.0L)
-		goto ovrf;
 
 	t = atan2l(2.0L * x, a) * 0.5L;
 	w = redupil(t);
 
 	t = y - 1.0L;
 	a = x2 + (t * t);
-	if (a == 0.0L)
-		goto ovrf;
 
 	t = y + 1.0L;
 	a = (x2 + (t * t)) / a;
-	w = w + (0.25L * logl(a)) * I;
-	return w;
-
-ovrf:
-	// FIXME
-	w = LDBL_MAX + LDBL_MAX * I;
+	w = CMPLXF(w, 0.25L * logl(a));
 	return w;
 }
 #endif