glsl/glcpp: Add an explanatory comment for "loc != NULL" check

Just reading the code, it looked like a bug that _define_object_macro had this
check, but _define_function_macro did not. Upon further reading, that's
because the check is to allow for our builtins to be defined, (and there are
no builtin function-like macros).

Add my new understanding as a comment to help the next reader.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

diff --git a/src/glsl/glcpp/glcpp-parse.y b/src/glsl/glcpp/glcpp-parse.y
index 9b753dd..f758345 100644 (file)
--- a/src/glsl/glcpp/glcpp-parse.y
+++ b/src/glsl/glcpp/glcpp-parse.y
@@ -1944,6 +1944,10 @@ _define_object_macro (glcpp_parser_t *parser,
 {
        macro_t *macro, *previous;
 
+       /* We define pre-defined macros before we've started parsing the
+         * actual file. So if there's no location defined yet, that's what
+         * were doing and we don't want to generate an error for using the
+         * reserved names. */
        if (loc != NULL)
                _check_for_reserved_macro_name(parser, loc, identifier);