Prefer fixed-width integer types instead of size_t

An implementation is free to use any representation it likes for size_t.
In general you'll have 32-bit size_t on 32-bit programs.

Fixes warnings:

openvdb_ax/openvdb_ax/codegen/StandardFunctions.cc: In instantiation of 'SeedType openvdb::v10_0::ax::codegen::{anonymous}::hashToSeed(size_t) [with SeedType = unsigned int; size_t = unsigned int]':
openvdb_ax/openvdb_ax/codegen/StandardFunctions.cc:978:76:   required from here
openvdb_ax/openvdb_ax/codegen/StandardFunctions.cc:56:19: warning: right shift count >= width of type [-Wshift-count-overflow]
   56 |     } while (hash >>= sizeof(SeedType) * 8);
      |              ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

and

openvdb_ax/openvdb_ax/test/integration/TestStandardFunctions.cc:1175:23: warning: right shift count >= width of type [-Wshift-count-overflow]
 1175 |         } while (hash >>= sizeof(uint32_t) * 8);
      |                  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Mathieu Malaterre <mathieu.malaterre@gmail.com>

Author: malaterre

openvdb_ax/openvdb_ax/codegen/StandardFunctions.cc

@@ -49,7 +49,7 @@ namespace
 // that fit into an unsigned int, and then shift those bytes out of the
 // hash. We repeat until we have no bits left in the hash.
 template <typename SeedType>
-inline SeedType hashToSeed(size_t hash) {
+inline SeedType hashToSeed(uint64_t hash) {
     SeedType seed = 0;
     do {
         seed ^= (SeedType) hash;
@@ -955,7 +955,7 @@ inline FunctionGroup::UniquePtr axrand32(const FunctionOptions& op)
             // (e.g. -0 and +0 must return the same hash value, etc). Other than these
             // special cases, this function will usually just copy the binary
             // representation of a float into the resultant `size_t`
-            const size_t hash = std::hash<double>()(seed);
+            const uint64_t hash = std::hash<double>()(seed);
 
             // Now that we have a reliable hash (with special floating-point cases taken
             // care of), we proceed to use this hash to seed a random number generator.

openvdb_ax/openvdb_ax/test/integration/TestStandardFunctions.cc

@@ -1166,7 +1166,7 @@ TestStandardFunctions::rand()
 void
 TestStandardFunctions::rand32()
 {
-    auto hashToSeed = [](size_t hash) ->
+    auto hashToSeed = [](uint64_t hash) ->
         std::mt19937::result_type
     {
         unsigned int seed = 0;