From 2d507c2fcdd5914d13a99399d80cbb9f85baf1d0 Mon Sep 17 00:00:00 2001
From: Stefan Fritsch <sf@apache.org>
Date: Sat, 30 Jan 2010 12:18:18 +0000
Subject: [PATCH] Allow the Define directive to undefine a variable by
 prefixing the argument with a '!'.

PR: 35350


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@904768 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES                  |  3 +++
 docs/manual/mod/core.xml |  6 ++++--
 server/core.c            | 29 ++++++++++++++++++++++++++---
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/CHANGES b/CHANGES
index 4d1ca4bda4..af191baea3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,9 @@
 
 Changes with Apache 2.3.6
 
+  *) Allow the Define directive to undefine a variable by prefixing the
+     argument with a '!'. PR 35350. [Stefan Fritsch]
+
   *) Make ap_pregsub(), used by AliasMatch and friends, use the same syntax
      for regex backreferences as mod_rewrite and mod_include: Remove the use
      of '&' as an alias for '$0' and allow to escape any character with a
diff --git a/docs/manual/mod/core.xml b/docs/manual/mod/core.xml
index 2bfdcb1a27..79e47416c6 100644
--- a/docs/manual/mod/core.xml
+++ b/docs/manual/mod/core.xml
@@ -596,8 +596,8 @@ which no other media type configuration could be found.
 
 <directivesynopsis>
 <name>Define</name>
-<description>Define the existence of a variable</description>
-<syntax>Define <var>parameter-name</var></syntax>
+<description>Define or undefine the existence of a variable</description>
+<syntax>Define [!]<var>parameter-name</var></syntax>
 <contextlist><context>server config</context></contextlist>
 
 <usage>
@@ -606,6 +606,8 @@ which no other media type configuration could be found.
     <p>This directive can be used to toggle the use of <directive module="core"
     type="section">IfDefine</directive> sections without needing to alter
     <code>-D</code> arguments in any startup scripts.</p>
+    <p>If the parameter-name is prefixed with a <code>!</code>, the definition
+    of the argument is removed.</p>
 </usage>
 </directivesynopsis>
 
diff --git a/server/core.c b/server/core.c
index 7edc0fe0b3..8d2e20579e 100644
--- a/server/core.c
+++ b/server/core.c
@@ -1104,7 +1104,7 @@ static const char *set_access_name(cmd_parms *cmd, void *dummy,
 static const char *set_define(cmd_parms *cmd, void *dummy,
                                    const char *optarg)
 {
-    char **newv;
+    int remove = 0;
 
     const char *err = ap_check_cmd_context(cmd,
                                            GLOBAL_ONLY);
@@ -1112,8 +1112,31 @@ static const char *set_define(cmd_parms *cmd, void *dummy,
         return err;
     }
 
-    newv = (char **)apr_array_push(ap_server_config_defines);
-    *newv = apr_pstrdup(cmd->pool, optarg);
+    if (*optarg == '!') {
+        remove = 1;
+        optarg++;
+    }
+
+    if (remove == 0 && !ap_exists_config_define(optarg)) {
+        char **newv = (char **)apr_array_push(ap_server_config_defines);
+        *newv = apr_pstrdup(cmd->pool, optarg);
+    }
+    else if (remove == 1) {
+        int i;
+        char **defines = (char **)ap_server_config_defines->elts;
+        for (i = 0; i < ap_server_config_defines->nelts; i++) {
+            if (strcmp(defines[i], optarg) == 0) {
+                if (i == ap_server_config_defines->nelts - 1) {
+                    apr_array_pop(ap_server_config_defines);
+                    break;
+                }
+                else {
+                    defines[i] = apr_array_pop(ap_server_config_defines);
+                    break;
+                }
+            }
+        }
+    }
 
     return NULL;
 }
-- 
2.40.0