add version comparision macro & test for it

Author: Wumpf

rerun_cpp/src/rerun/c/sdk_info.h

@@ -12,3 +12,17 @@
 
 /// Patch version of the Rerun C SDK.
 #define RERUN_SDK_HEADER_VERSION_PATCH 0
+
+/// Is the Rerun library version greater or equal to this?
+///
+/// Example usage:
+/// ```
+/// #if RERUN_VERSION_GE(0, 18, 0)
+///    // Use features from Rerun 0.18
+/// #endif
+/// ```
+#define RERUN_VERSION_GE(major, minor, patch)                                                      \
+    ((major) == RERUN_SDK_HEADER_VERSION_MAJOR                                                     \
+         ? ((minor) == RERUN_SDK_HEADER_VERSION_MINOR ? (patch) <= RERUN_SDK_HEADER_VERSION_PATCH  \
+                                                      : (minor) <= RERUN_SDK_HEADER_VERSION_MINOR) \
+         : (major) <= RERUN_SDK_HEADER_VERSION_MAJOR)

rerun_cpp/tests/sdk_info.cpp

@@ -0,0 +1,37 @@
+#include <rerun.hpp>
+
+static_assert(RERUN_VERSION_GE(0, 18, 0), "Rerun version was expected to be at least 0.18.0");
+static_assert(
+    RERUN_VERSION_GE(
+        RERUN_SDK_HEADER_VERSION_MAJOR, RERUN_SDK_HEADER_VERSION_MINOR,
+        RERUN_SDK_HEADER_VERSION_PATCH
+    ),
+    "Rerun version is equal to this version."
+);
+static_assert(
+    !RERUN_VERSION_GE(
+        RERUN_SDK_HEADER_VERSION_MAJOR, RERUN_SDK_HEADER_VERSION_MINOR,
+        RERUN_SDK_HEADER_VERSION_PATCH + 1
+    ),
+    "Rerun version is not greater than this version."
+);
+static_assert(
+    !RERUN_VERSION_GE(
+        RERUN_SDK_HEADER_VERSION_MAJOR, RERUN_SDK_HEADER_VERSION_MINOR + 1,
+        RERUN_SDK_HEADER_VERSION_PATCH
+    ),
+    "Rerun version is not greater than this version."
+);
+static_assert(
+    !RERUN_VERSION_GE(
+        RERUN_SDK_HEADER_VERSION_MAJOR + 1, RERUN_SDK_HEADER_VERSION_MINOR,
+        RERUN_SDK_HEADER_VERSION_PATCH
+    ),
+    "Rerun version is not greater than this version."
+);
+
+#if RERUN_VERSION_GE(0, 18, 0)
+static_assert(true, "Rerun can be used in a macro.");
+#else
+static_assert(false, "Rerun can be used in a macro, but we shouldn't be able to get here.");
+#endif