Fix size_t -> int -> size_t round trip in Cycles

There are two things achieved by this change:

- No possible downcast of size_t to int when calculating motion steps.
- Disambiguate call to `min()` which was for some reason considered
  ambiguous on 32bit platforms `min(int, unsigned int)`.
- Do the same for the `max()` call to keep them symmetrical.

On an implementation side the `min()` is defined for a fixed width
integer type to disambiguate uint from size_t on 32bit platforms,
and yet be able to use it for 32bit operands on 64bit platforms without
upcast.

This ended up in a bit bigger change as the conditional compile-in of
functions is easiest if the functions is templated. Making the functions
templated required to remove the other source of ambiguity which is
`algorithm.h` which was pulling min/max from std.

Now it is the `math.h` which is the source of truth for min/max.
It was only one place which was relying on `algorithm.h` for these
functions, hence the choice of `math.h` as the safest and least
intrusive.

Fixes 32bit platforms (such as i386) in Debian package build system.

Differential Revision: https://developer.blender.org/D14062

4 files changed, 10 insertions, 10 deletions

diff --git a/intern/cycles/scene/hair.cpp b/intern/cycles/scene/hair.cpp
index 2951a609ae9..9ac502e2727 100644
--- a/intern/cycles/scene/hair.cpp
+++ b/intern/cycles/scene/hair.cpp
@@ -119,7 +119,7 @@ void Hair::Curve::motion_keys(const float3 *curve_keys,
 {
   /* Figure out which steps we need to fetch and their interpolation factor. */
   const size_t max_step = num_steps - 1;
-  const size_t step = min((int)(time * max_step), max_step - 1);
+  const size_t step = std::min((size_t)(time * max_step), max_step - 1);
   const float t = time * max_step - step;
   /* Fetch vertex coordinates. */
   float4 curr_keys[2];
@@ -147,7 +147,7 @@ void Hair::Curve::cardinal_motion_keys(const float3 *curve_keys,
 {
   /* Figure out which steps we need to fetch and their interpolation factor. */
   const size_t max_step = num_steps - 1;
-  const size_t step = min((int)(time * max_step), max_step - 1);
+  const size_t step = min((size_t)(time * max_step), max_step - 1);
   const float t = time * max_step - step;
   /* Fetch vertex coordinates. */
   float4 curr_keys[4];
@@ -191,8 +191,8 @@ void Hair::Curve::keys_for_step(const float3 *curve_keys,
                                 size_t k1,
                                 float4 r_keys[2]) const
 {
-  k0 = max(k0, 0);
-  k1 = min(k1, num_keys - 1);
+  k0 = max(k0, (size_t)0);
+  k1 = min(k1, (size_t)(num_keys - 1));
   const size_t center_step = ((num_steps - 1) / 2);
   if (step == center_step) {
     /* Center step: regular key location. */
@@ -237,8 +237,8 @@ void Hair::Curve::cardinal_keys_for_step(const float3 *curve_keys,
                                          size_t k3,
                                          float4 r_keys[4]) const
 {
-  k0 = max(k0, 0);
-  k3 = min(k3, num_keys - 1);
+  k0 = max(k0, (size_t)0);
+  k3 = min(k3, (size_t)(num_keys - 1));
   const size_t center_step = ((num_steps - 1) / 2);
   if (step == center_step) {
     /* Center step: regular key location. */
diff --git a/intern/cycles/scene/light.cpp b/intern/cycles/scene/light.cpp
index 83e531f42ef..415c4044aee 100644
--- a/intern/cycles/scene/light.cpp
+++ b/intern/cycles/scene/light.cpp
@@ -606,8 +606,8 @@ void LightManager::device_update_background(Device *device,
       ImageMetaData metadata;
       if (!env->handle.empty()) {
         ImageMetaData metadata = env->handle.metadata();
-        environment_res.x = max(environment_res.x, metadata.width);
-        environment_res.y = max(environment_res.y, metadata.height);
+        environment_res.x = max(environment_res.x, (int)metadata.width);
+        environment_res.y = max(environment_res.y, (int)metadata.height);
       }
     }
     if (node->type == SkyTextureNode::get_node_type()) {
diff --git a/intern/cycles/scene/mesh.cpp b/intern/cycles/scene/mesh.cpp
index c381d7a54ff..f53dca88ee0 100644
--- a/intern/cycles/scene/mesh.cpp
+++ b/intern/cycles/scene/mesh.cpp
@@ -53,7 +53,7 @@ void Mesh::Triangle::motion_verts(const float3 *verts,
 {
   /* Figure out which steps we need to fetch and their interpolation factor. */
   const size_t max_step = num_steps - 1;
-  const size_t step = min((int)(time * max_step), max_step - 1);
+  const size_t step = min((size_t)(time * max_step), max_step - 1);
   const float t = time * max_step - step;
   /* Fetch vertex coordinates. */
   float3 curr_verts[3];
diff --git a/intern/cycles/scene/pointcloud.cpp b/intern/cycles/scene/pointcloud.cpp
index 4f88fe9db3d..6356a5030f3 100644
--- a/intern/cycles/scene/pointcloud.cpp
+++ b/intern/cycles/scene/pointcloud.cpp
@@ -55,7 +55,7 @@ float4 PointCloud::Point::motion_key(const float3 *points,
   /* Figure out which steps we need to fetch and their
    * interpolation factor. */
   const size_t max_step = num_steps - 1;
-  const size_t step = min((int)(time * max_step), max_step - 1);
+  const size_t step = min((size_t)(time * max_step), max_step - 1);
   const float t = time * max_step - step;
   /* Fetch vertex coordinates. */
   const float4 curr_key = point_for_step(