And FINALLY fixed the NULL name error in uiRegisterControlType().

common/controls.c

@@ -48,6 +48,10 @@ uint32_t uiRegisterControlType(const char *name, const uiControlVtable *vtable,
 
 	if (!uiprivCheckInitializedAndThread())
 		return 0;
+	if (name == NULL) {
+		uiprivProgrammerErrorNullPointer("name", uiprivFunc);
+		return 0;
+	}
 	if (vtable == NULL) {
 		uiprivProgrammerErrorNullPointer("uiControlVtable", uiprivFunc);
 		return 0;

doc/controls.md

@@ -47,7 +47,7 @@ uint32_t uiRegisterControlType(const char *name, const uiControlVtable *vtable,
 
 `uiRegisterControlType()` registers a new `uiControl` type with the given vtables and returns its ID as passed to `uiNewControl()`. `implDataSize` is the size of the implementation data struct that is created by `uiNewControl()`.
 
-Each type has a name, passed in the `name` parameter. The type name is only used for debugging and error reporting purposes. The type name is copied into libui-internal memory; the `name` pointer passed to `uiRegisterControlType()` is not used after it returns.
+Each type has a name, passed in the `name` parameter. The type name is only used for debugging and error reporting purposes. The type name is copied into libui-internal memory; the `name` pointer passed to `uiRegisterControlType()` is not used after it returns. It is a programmer error to specify `NULL` for `name`. (TODO anything else? Empty string? Duplicate name?)
 
 `uiControlVtable` describes the functions of a `uiControl` common between platforms, and is discussed on this page. `uiControlOSVtable` describes functionst hat vary from OS to OS, and are described in the respective OS-specific uiControl implementation pages. The two vtables are copied into libui-internal memory; the vtable pointers passed to `uiRegisterControlType()` are not used after it returns.
 

test/controls_errors.cpp

@@ -7,7 +7,7 @@ static const struct checkErrorCase cases[] = {
 		[](void) {
 			uiRegisterControlType(NULL, NULL, NULL, 0);
 		},
-		"uiRegisterControlType(): invalid null pointer for uiControlOSVtable",
+		"uiRegisterControlType(): invalid null pointer for name",
 	},
 	{
 		"uiRegisterControlType() with NULL vtable",