1 files changed, 22 insertions, 1 deletions
diff --git a/lib9p/idl.gen b/lib9p/idl.gen
index 31f6527..47ca49a 100755
--- a/lib9p/idl.gen
+++ b/lib9p/idl.gen
@@ -62,7 +62,8 @@ def c_ver_ifdef(versions: set[str]) -> str:
 
 def c_ver_cond(versions: set[str]) -> str:
     if len(versions) == 1:
-        return f"(ctx->ctx->version=={c_ver_enum(next(v for v in versions))})"
+        v = next(v for v in versions)
+        return f"is_ver(ctx, {v.replace('.', '_')})"
     return "( " + (" || ".join(c_ver_cond({v}) for v in sorted(versions))) + " )"
 
 
@@ -318,12 +319,32 @@ def gen_c(versions: set[str], typs: list[idl.Type]) -> str:
 #include "internal.h"
 """
 
+    # utilities ################################################################
+    ret += f"""
+/* utilities ******************************************************************/
+"""
+
     def used(arg: str) -> str:
         return arg
 
     def unused(arg: str) -> str:
         return f"LM_UNUSED({arg})"
 
+    ret += "\n"
+    ret += "/**\n"
+    ret += f" * is_ver(ctx, ver) is essentially `(ctx->ctx->version == {idprefix.upper()}VER_##ver)`,\n"
+    ret += f" * but compiles correctly (to `false`) even if `{idprefix.upper()}VER_##ver` isn't defined\n"
+    ret += " * (because `!CONFIG_9P_ENABLE_##ver`).  This is useful when `||`ing\n"
+    ret += " * several version checks together.\n"
+    ret += " */\n"
+    ret += "#define is_ver(ctx, ver) _is_ver_##ver(ctx->ctx->version)\n"
+    for v in sorted(versions):
+        ret += f"#if CONFIG_9P_ENABLE_{v.replace('.', '_')}\n"
+        ret += f"\t#define _is_ver_{v.replace('.', '_')}(v) (v == {c_ver_enum(v)})\n"
+        ret += "#else\n"
+        ret += f"\t#define _is_ver_{v.replace('.', '_')}(v) false\n"
+        ret += "#endif\n"
+
     # strings ##################################################################
     ret += f"""
 /* strings ********************************************************************/