CTest: add safe conversion from cmDuration to integer types

A problem area by recent refactoring of time to std::chrono has been the
unsafe conversion from duration<double> to std::chrono::seconds, which
is of an unspecified integer type.

This commit adds a template function that for a given type provides a
safe conversion, effectively clamping a duration<double> into what fits
safely in that type. A specialisation for int and unsigned int are
provided.

It changes the protential problem areas to use this safe function.

1 files changed, 16 insertions, 0 deletions

diff --git a/Source/cmDuration.h b/Source/cmDuration.h
index 5f73585..6df1455 100644
--- a/Source/cmDuration.h
+++ b/Source/cmDuration.h
@@ -6,3 +6,19 @@
 #include <ratio>
 
 typedef std::chrono::duration<double, std::ratio<1>> cmDuration;
+
+/*
+ * This function will return number of seconds in the requested type T.
+ *
+ * A duration_cast from duration<double> to duration<T> will not yield what
+ * one might expect if the double representation does not fit into type T.
+ * This function aims to safely convert, by clamping the double value between
+ * the permissible valid values for T.
+ */
+template <typename T>
+T cmDurationTo(const cmDuration& duration);
+
+#ifndef CMDURATION_CPP
+extern template int cmDurationTo<int>(const cmDuration&);
+extern template unsigned int cmDurationTo<unsigned int>(const cmDuration&);
+#endif