Mesa (main): glsl/glcpp: make sure to expand new token after concatenation

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Module: Mesa
Branch: main
Commit: d2711f9b61a4c2c7fb2f1fe60bc9d02eefc53738
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d2711f9b61a4c2c7fb2f1fe60bc9d02eefc53738

Author: Timothy Arceri <tarceri at itsqueeze.com>
Date:   Tue Dec  7 15:35:48 2021 +1100

glsl/glcpp: make sure to expand new token after concatenation

Previously the code was using a hack to change the token type from
INDETIFIER -> OTHER in order to avoid getting in an infinite loop
expanding the tokens. This worked ok until we got to a paste where
the replacement parameters had already had their type changed
to OTHER because the newly created paste token would then
inherit the OTHER type and never get expanded inself.

For example with the follow code:

   #define STEP_ONE() \
	out_Color = vec4(0.0,1.0,0.0,1.0)

   #define GLUE(x,y) x ## _ ## y
   #define EVALUATE(x,y)  GLUE(x,y)
   #define STEP(stepname) EVALUATE(STEP, stepname)()
   #define PERFORM_RAYCASTING_STEP STEP(ONE)

This would get all the way to expanding PERFORM_RAYCASTING_STEP to
STEP_ONE() but because it was created via the paste `x ## _ ## y`
it would never get any further.

To fix this we remove the OTHER hack and instead just track if the
token has already been handled via a bool value `explanding`.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5724

Fixes: 28842c2331e6 ("glcpp: Implement token pasting for non-function-like macros")

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14101>

---

 src/compiler/glsl/glcpp/glcpp-parse.y | 11 +++++++++--
 src/compiler/glsl/glcpp/glcpp.h       |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/compiler/glsl/glcpp/glcpp-parse.y b/src/compiler/glsl/glcpp/glcpp-parse.y
index 33aba1b6aa0..ab0fd6076c4 100644
--- a/src/compiler/glsl/glcpp/glcpp-parse.y
+++ b/src/compiler/glsl/glcpp/glcpp-parse.y
@@ -1057,6 +1057,7 @@ _token_create_str(glcpp_parser_t *parser, int type, char *str)
    token = linear_alloc_child(parser->linalloc, sizeof(token_t));
    token->type = type;
    token->value.str = str;
+   token->expanding = false;
 
    return token;
 }
@@ -1069,6 +1070,7 @@ _token_create_ival(glcpp_parser_t *parser, int type, int ival)
    token = linear_alloc_child(parser->linalloc, sizeof(token_t));
    token->type = type;
    token->value.ival = ival;
+   token->expanding = false;
 
    return token;
 }
@@ -1958,6 +1960,10 @@ _glcpp_parser_expand_node(glcpp_parser_t *parser, token_node_t *node,
    struct hash_entry *entry;
    macro_t *macro;
 
+   /* If token is already being expanded return to avoid an infinite loop */
+   if (token->expanding)
+      return NULL;
+
    /* We only expand identifiers */
    if (token->type != IDENTIFIER) {
       return NULL;
@@ -1988,14 +1994,15 @@ _glcpp_parser_expand_node(glcpp_parser_t *parser, token_node_t *node,
    /* Finally, don't expand this macro if we're already actively
     * expanding it, (to avoid infinite recursion). */
    if (_parser_active_list_contains (parser, identifier)) {
-      /* We change the token type here from IDENTIFIER to OTHER to prevent any
+      /* We change the `expanding` bool to true to prevent any
        * future expansion of this unexpanded token. */
       char *str;
       token_list_t *expansion;
       token_t *final;
 
       str = linear_strdup(parser->linalloc, token->value.str);
-      final = _token_create_str(parser, OTHER, str);
+      final = _token_create_str(parser, token->type, str);
+      final->expanding = true;
       expansion = _token_list_create(parser);
       _token_list_append(parser, expansion, final);
       return expansion;
diff --git a/src/compiler/glsl/glcpp/glcpp.h b/src/compiler/glsl/glcpp/glcpp.h
index 38ea3949cd6..b797433adb1 100644
--- a/src/compiler/glsl/glcpp/glcpp.h
+++ b/src/compiler/glsl/glcpp/glcpp.h
@@ -103,6 +103,7 @@ do {								\
 } while (0)
 
 struct token {
+	bool expanding;
 	int type;
 	YYSTYPE value;
 	YYLTYPE location;