From 35173060ff23af484d47c3f110da204cedfe1724 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Sat, 14 Feb 2009 01:44:07 -0500
Subject: [PATCH] Added #undef directive to preprocessor.

---
 mojoshader_preprocessor.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/mojoshader_preprocessor.c b/mojoshader_preprocessor.c
index 7d9385cf..a029752e 100644
--- a/mojoshader_preprocessor.c
+++ b/mojoshader_preprocessor.c
@@ -296,7 +296,6 @@ static int remove_define(Context *ctx, const char *sym)
         bucket = bucket->next;
     } // while
 
-    failf(ctx, "'%s' not defined", sym);
     return 0;
 } // remove_define
 
@@ -675,6 +674,31 @@ static void handle_pp_error(Context *ctx)
 } // handle_pp_error
 
 
+static void handle_pp_undef(Context *ctx)
+{
+    IncludeState *state = ctx->include_stack;
+
+    if (preprocessor_internal_lexer(state) != TOKEN_IDENTIFIER)
+    {
+        fail(ctx, "Macro names must be indentifiers");
+        return;
+    } // if
+
+    const unsigned int len = ((unsigned int) (state->source-state->token));
+    char *sym = (char *) alloca(len);
+    memcpy(sym, state->token, len-1);
+    sym[len-1] = '\0';
+
+    if (!require_newline(state))
+    {
+        fail(ctx, "Invalid #undef directive");
+        return;
+    } // if
+
+    remove_define(ctx, sym);
+} // handle_pp_undef
+
+
 static inline const char *_preprocessor_nexttoken(Preprocessor *_ctx,
                                              unsigned int *_len, Token *_token)
 {
@@ -700,7 +724,6 @@ static inline const char *_preprocessor_nexttoken(Preprocessor *_ctx,
 
         // !!! FIXME: todo.
         // TOKEN_PP_DEFINE,
-        // TOKEN_PP_UNDEF,
         // TOKEN_PP_IF,
         // TOKEN_PP_IFDEF,
         // TOKEN_PP_IFNDEF,
@@ -740,6 +763,12 @@ static inline const char *_preprocessor_nexttoken(Preprocessor *_ctx,
             continue;  // will return at top of loop.
         } // else if
 
+        else if (token == TOKEN_PP_UNDEF)
+        {
+            handle_pp_undef(ctx);
+            continue;  // will return at top of loop.
+        } // else if
+
         // !!! FIXME: check for ((Token) '\n'), so we know if a preprocessor
         // !!! FIXME:  directive started a line.