[PATCH 0/1] MR4475: gdiplus: Avoid computation overflow and underflow by using hypotf

[Bartosz Kosiorek (＠gang65)]

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=45123

By using sqrt(a * a + b * b), for large (or small) a or b, there is a possibility of overflow (underflow),
although the result itself is not that big to cause overflow.

To overcome this problem, there are implementations of hypotenuse that do not use power of 2,
and use other methods to calculate the result.
To calculate a ⊕ b, you can easily use hypotf(a,b).

https://en.cppreference.com/w/cpp/numeric/math/hypot

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/4475

[PATCH 1/1] gdiplus: Avoid computation overflow and underflow by using hypotf

[Bartosz Kosiorek]

From: Bartosz Kosiorek <gang65(a)poczta.onet.pl>

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=45123

By using sqrt(a * a + b * b), for large (or small) a or b, there is a possibility of overflow (underflow),
although the result itself is not that big to cause overflow.

To overcome this problem, there are implementations of hypotenuse that do not use power of 2,
and use other methods to calculate the result.
To calculate a ⊕ b, you can easily use hypotf(a,b).

https://en.cppreference.com/w/cpp/numeric/math/hypot
---
 dlls/gdiplus/graphicspath.c | 40 ++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/dlls/gdiplus/graphicspath.c b/dlls/gdiplus/graphicspath.c
index 63f120a6aba..7643191d1dc 100644
--- a/dlls/gdiplus/graphicspath.c
+++ b/dlls/gdiplus/graphicspath.c
@@ -201,7 +201,7 @@ static BOOL flatten_bezier(path_list_node_t *start, REAL x2, REAL y2, REAL x3, R
          *     x0(y2 - y1) + y0(x1 - x2) + (x2*y1 - x1*y2)
          */
         area_triangle = (pt.Y - pt_st.Y)*mp[2].X + (pt_st.X - pt.X)*mp[2].Y + (pt_st.Y*pt.X - pt_st.X*pt.Y);
-        distance_start_end = sqrtf(powf(pt.Y - pt_st.Y, 2.0) + powf(pt_st.X - pt.X, 2.0));
+        distance_start_end = hypotf((pt.Y - pt_st.Y), (pt_st.X - pt.X));
         if(fabs(area_triangle) <= (0.5 * flatness * distance_start_end)){
             continue;
         }
@@ -1867,7 +1867,7 @@ static void add_bevel_point(const GpPointF *endpoint, const GpPointF *nextpoint,
 {
     REAL segment_dy = nextpoint->Y-endpoint->Y;
     REAL segment_dx = nextpoint->X-endpoint->X;
-    REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+    REAL segment_length = hypotf(segment_dy, segment_dx);
     REAL distance = pen_width / 2.0;
     REAL bevel_dx, bevel_dy;
 
@@ -1902,16 +1902,16 @@ static void widen_joint(const GpPointF *p1, const GpPointF *p2, const GpPointF *
     case LineJoinMiterClipped:
         if ((p2->X - p1->X) * (p3->Y - p1->Y) > (p2->Y - p1->Y) * (p3->X - p1->X))
         {
-            float distance = pen_width / 2.0;
-            float length_0 = sqrtf((p2->X-p1->X)*(p2->X-p1->X)+(p2->Y-p1->Y)*(p2->Y-p1->Y));
-            float length_1 = sqrtf((p3->X-p2->X)*(p3->X-p2->X)+(p3->Y-p2->Y)*(p3->Y-p2->Y));
-            float dx0 = distance * (p2->X - p1->X) / length_0;
-            float dy0 = distance * (p2->Y - p1->Y) / length_0;
-            float dx1 = distance * (p3->X - p2->X) / length_1;
-            float dy1 = distance * (p3->Y - p2->Y) / length_1;
-            float det = (dy0*dx1 - dx0*dy1);
-            float dx = (dx0*dx1*(dx0-dx1) + dy0*dy0*dx1 - dy1*dy1*dx0)/det;
-            float dy = (dy0*dy1*(dy0-dy1) + dx0*dx0*dy1 - dx1*dx1*dy0)/det;
+            REAL distance = pen_width / 2.0;
+            REAL length_0 = hypotf((p2->X - p1->X), (p2->Y - p1->Y));
+            REAL length_1 = hypotf((p3->X - p2->X), (p3->Y - p2->Y));
+            REAL dx0 = distance * (p2->X - p1->X) / length_0;
+            REAL dy0 = distance * (p2->Y - p1->Y) / length_0;
+            REAL dx1 = distance * (p3->X - p2->X) / length_1;
+            REAL dy1 = distance * (p3->Y - p2->Y) / length_1;
+            REAL det = (dy0 * dx1 - dx0 * dy1);
+            REAL dx = (dx0 * dx1 * (dx0 - dx1) + dy0 * dy0 * dx1 - dy1 * dy1 * dx0) / det;
+            REAL dy = (dy0 * dy1 * (dy0 - dy1) + dx0 * dx0 * dy1 - dx1 * dx1 * dy0) / det;
             if (dx*dx + dy*dy < pen->miterlimit*pen->miterlimit * distance*distance)
             {
                 *last_point = add_path_list_node(*last_point, p2->X + dx,
@@ -1954,7 +1954,7 @@ static void widen_cap(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL distance = pen_width / 2.0;
         REAL bevel_dx, bevel_dy;
         REAL extend_dx, extend_dy;
@@ -1989,7 +1989,7 @@ static void widen_cap(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL distance = pen_width / 2.0;
         REAL dx, dy, dx2, dy2;
         const REAL control_point_distance = 0.5522847498307935; /* 4/3 * (sqrt(2) - 1) */
@@ -2034,7 +2034,7 @@ static void widen_cap(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL distance = pen_width / 2.0;
         REAL dx, dy;
 
@@ -2074,7 +2074,7 @@ static void add_anchor(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL distance = pen_width / sqrtf(2.0);
         REAL par_dx, par_dy;
         REAL perp_dx, perp_dy;
@@ -2099,7 +2099,7 @@ static void add_anchor(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL dx, dy, dx2, dy2;
         const REAL control_point_distance = 0.55228475; /* 4/3 * (sqrt(2) - 1) */
 
@@ -2151,7 +2151,7 @@ static void add_anchor(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y-endpoint->Y;
         REAL segment_dx = nextpoint->X-endpoint->X;
-        REAL segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL par_dx, par_dy;
         REAL perp_dx, perp_dy;
 
@@ -2175,7 +2175,7 @@ static void add_anchor(const GpPointF *endpoint, const GpPointF *nextpoint,
     {
         REAL segment_dy = nextpoint->Y - endpoint->Y;
         REAL segment_dx = nextpoint->X - endpoint->X;
-        REAL segment_length = sqrtf(segment_dy * segment_dy + segment_dx * segment_dx);
+        REAL segment_length = hypotf(segment_dy, segment_dx);
         REAL par_dx = pen_width * segment_dx / segment_length;
         REAL par_dy = pen_width * segment_dy / segment_length;
         REAL perp_dx = -par_dy;
@@ -2407,7 +2407,7 @@ static void widen_dashed_figure(GpPath *path, int start, int end, int closed,
 
         segment_dy = path->pathdata.Points[j].Y - path->pathdata.Points[i].Y;
         segment_dx = path->pathdata.Points[j].X - path->pathdata.Points[i].X;
-        segment_length = sqrtf(segment_dy*segment_dy + segment_dx*segment_dx);
+        segment_length = hypotf(segment_dy, segment_dx);
         segment_pos = 0.0;
 
         while (1)
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/4475