types/description: add a validation specialisation

types/description.cpp

@@ -37,3 +37,54 @@ cruft::types::operator<< (std::ostream &os, cruft::types::description val)
               << ", alignment: " << val.alignment
               << " }";
 }
+
+
+///////////////////////////////////////////////////////////////////////////////
+#include "../debug/validate.hpp"
+#include <iostream>
+
+//-----------------------------------------------------------------------------
+template <>
+struct cruft::debug::validator<cruft::types::description> {
+    static bool is_valid (cruft::types::description const&);
+};
+
+
+//-----------------------------------------------------------------------------
+bool
+cruft::debug::validator<cruft::types::description>::is_valid (
+    cruft::types::description const &val
+) {
+    switch (val.category) {
+    // Ensure types that look fundamental might have a chance of being
+    // represented in hardware.
+    case cruft::types::category::UNSIGNED:
+    case cruft::types::category::SIGNED:
+    case cruft::types::category::REAL:
+    case cruft::types::category::BOOL:
+        // Most numbers are only realistic if they're powers of two; it's not
+        // a requirement, it's just stupid suspicious.
+        //
+        // Though arity of 3 is common for 3D points so we make an exception
+        // here.
+        WARN_RETURN (!is_pow2 (val.width), false);
+        WARN_RETURN (!is_pow2 (val.arity) && val.arity != 3, false);
+        WARN_RETURN (!is_pow2 (val.alignment), false);
+
+        // Restrict bounds of native type constants to values that correspond
+        // to the hardware we tend to work on.
+        //
+        // Again, this is mostly for plausibilty rather than anything else.
+        // Feel free to make this less restrictive.
+        WARN_RETURN (val.width == 0 || val.width > 8, false);
+        WARN_RETURN (val.arity == 0 || val.arity > 16, false);
+        WARN_RETURN (val.alignment == 0 || val.alignment > 64, false);
+
+    // All bets are off. Have fun.
+    case cruft::types::category::NONE:
+        return true;
+    }
+
+    WARN ("Unknown value category");
+    return false;
+}