tpers: avoid division by zero

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=14342
Credit to OSS Fuzz

1 files changed, 9 insertions, 7 deletions

diff --git a/src/projections/nsper.cpp b/src/projections/nsper.cpp
index a0bb5686..37938924 100644
--- a/src/projections/nsper.cpp
+++ b/src/projections/nsper.cpp
@@ -96,7 +96,7 @@ static PJ_XY s_forward (PJ_LP lp, PJ *P) {           /* Spheroidal, forward */
 static PJ_LP s_inverse (PJ_XY xy, PJ *P) {           /* Spheroidal, inverse */
     PJ_LP lp = {0.0,0.0};
     struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
-    double  rh, cosz, sinz;
+    double  rh;
 
     if (Q->tilt) {
         double bm, bq, yt;
@@ -108,16 +108,18 @@ static PJ_LP s_inverse (PJ_XY xy, PJ *P) {           /* Spheroidal, inverse */
         xy.y = bq * Q->cg - bm * Q->sg;
     }
     rh = hypot(xy.x, xy.y);
-    if ((sinz = 1. - rh * rh * Q->pfact) < 0.) {
-        proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
-        return lp;
-    }
-    sinz = (Q->p - sqrt(sinz)) / (Q->pn1 / rh + rh / Q->pn1);
-    cosz = sqrt(1. - sinz * sinz);
     if (fabs(rh) <= EPS10) {
         lp.lam = 0.;
         lp.phi = P->phi0;
     } else {
+        double cosz, sinz;
+        sinz = 1. - rh * rh * Q->pfact;
+        if (sinz < 0.) {
+            proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+            return lp;
+        }
+        sinz = (Q->p - sqrt(sinz)) / (Q->pn1 / rh + rh / Q->pn1);
+        cosz = sqrt(1. - sinz * sinz);
         switch (Q->mode) {
         case OBLIQ:
             lp.phi = asin(cosz * Q->sinph0 + xy.y * sinz * Q->cosph0 / rh);