Bug #20748: Configuration files should not be read more than once

A user could not override system-wide settings in their ~/.my.cnf,
because the DEFAULT_SYSCONFDIR was being searched last.  Also, in
some configurations (especially when the --sysconfdir compile-time
option is set to /etc or /etc/mysql), the system-wide my.cnf file
was read multiple times, causing confusion and potential problems.

Rearrange default directories to conform to the manual and logic.
Move --sysconfdir=<path> (DEFAULT_SYSCONFDIR) from the last default
directory to the middle of the list.  $HOME/.my.cnf should be last,
so the user is able to override the system-wide settings.

Change init_default_directories() to remove duplicates from the
list.


include/my_sys.h:
  Add array_append_string_unique(), from mf_arr_appstr.c
libmysql/Makefile.shared:
  Add new mf_arr_appstr.lo object
mysys/CMakeLists.txt:
  Add new mf_arr_appstr.c source.
mysys/Makefile.am:
  Add new mf_arr_appstr.c source.
mysys/default.c:
  Change order in which defaults files are added to default_directories,
  in order to conform to the manual (and to common sense).  This fixes
  a particularly bad problem on Unix, where ~/.my.cnf was read before
  /usr/local/etc/my.cnf.
  
  Also, don't add duplicate entries; move the existing entry to the
  end of the list instead.
  
  
  Here is a comparison of the order of defaults files, BEFORE and AFTER
  this patch.
  
  On Windows:
  
  BEFORE:  C:\, GetWindowsDirectory(), GetSystemWindowsDirectory(),
           $MYSQL_HOME, defaults-extra-file, INSTALLDIR
  
  AFTER:  GetSystemWindowsDirectory(), GetWindowsDirectory(), C:\,
          INSTALLDIR, $MYSQL_HOME, defaults-extra-file
  
  GetSystemWindowsDirectory() is moved before GetWindowsDirectory() because
  the former is shared by all Terminal Services users, while the latter is
  private for each user.
  
  
  On Netware (no change):
  
  BEFORE:  sys:/etc/, $MYSQL_HOME, defaults-extra-file
  
  AFTER:  sys:/etc, $MYSQL_HOME, defaults-extra-file
  
  
  On OS/2:
  
  BEFORE:  $ETC, /etc, $MYSQL_HOME, defaults-extra-file
  
  AFTER:  /etc, $ETC, $MYSQL_HOME, defaults-extra-file
  
  
  On everything else (general Unix):
  
  BEFORE:  /etc, $MYSQL_HOME, defaults-extra-file, ~/, --sysconfdir
  
  AFTER:  /etc/, --sysconfdir, $MYSQL_HOME, defaults-extra-file, ~/
  
  The BEFORE code added --sysconfdir on all systems, but only the
  Unix build system actually defined a value for it.
mysys/mf_arr_appstr.c:
  BitKeeper file /home/tsmith/m/bk/build/50-b20748/mysys/mf_arr_appstr.c

1 files changed, 129 insertions, 63 deletions

diff --git a/mysys/default.c b/mysys/default.c
index aff38b6af0b..74d016ce53c 100644
--- a/mysys/default.c
+++ b/mysys/default.c
@@ -47,7 +47,7 @@ char *my_defaults_extra_file=0;
 
 /* Which directories are searched for options (and in which order) */
 
-#define MAX_DEFAULT_DIRS 7
+#define MAX_DEFAULT_DIRS 6
 const char *default_directories[MAX_DEFAULT_DIRS + 1];
 
 #ifdef __WIN__
@@ -83,7 +83,22 @@ static int search_default_file_with_ext(Process_option_func func,
                                         void *func_ctx,
 					const char *dir, const char *ext,
 					const char *config_file, int recursion_level);
-static void init_default_directories();
+
+
+
+/**
+  Create the list of default directories.
+
+  @details
+  On all systems, if a directory is already in the list, it will be moved
+  to the end of the list.  This avoids reading defaults files multiple times,
+  while ensuring the correct precedence.
+
+  @return void
+*/
+
+static void (*init_default_directories)();
+
 
 static char *remove_end_comment(char *ptr);
 
@@ -913,6 +928,25 @@ void print_defaults(const char *conf_file, const char **groups)
 #include <help_end.h>
 
 
+#define ADD_DIRECTORY(DIR) \
+  do { \
+    my_bool rc= \
+      array_append_string_unique((DIR), default_directories, \
+                                 array_elements(default_directories)); \
+    DBUG_ASSERT(rc == FALSE);                   /* Success */ \
+  } while (0)
+
+
+#define ADD_COMMON_DIRECTORIES() \
+  do { \
+    char *env; \
+    if ((env= getenv(STRINGIFY_ARG(DEFAULT_HOME_ENV)))) \
+      ADD_DIRECTORY(env); \
+    /* Placeholder for --defaults-extra-file=<path> */ \
+    ADD_DIRECTORY(""); \
+  } while (0)
+
+
 #ifdef __WIN__
 /*
   This wrapper for GetSystemWindowsDirectory() will dynamically bind to the
@@ -947,73 +981,33 @@ static uint my_get_system_windows_directory(char *buffer, uint size)
   }
   return count;
 }
-#endif
 
 
-/*
-  Create the list of default directories.
+/**
+  Initialize default directories for Microsoft Windows
 
-  On Microsoft Windows, this is:
-    1. C:/
+  @details
+    1. GetSystemWindowsDirectory()
     2. GetWindowsDirectory()
-    3. GetSystemWindowsDirectory()
-    4. getenv(DEFAULT_HOME_ENV)
-    5. Directory above where the executable is located
-    6. ""
-    7. --sysconfdir=<path>
-
-  On Novell NetWare, this is:
-    1. sys:/etc/
-    2. getenv(DEFAULT_HOME_ENV)
-    3. ""
-    4. --sysconfdir=<path>
-
-  On OS/2, this is:
-    1. getenv(ETC)
-    2. /etc/
-    3. getenv(DEFAULT_HOME_ENV)
-    4. ""
-    5. "~/"
-    6. --sysconfdir=<path>
-
-  Everywhere else, this is:
-    1. /etc/
-    2. getenv(DEFAULT_HOME_ENV)
-    3. ""
-    4. "~/"
-    5. --sysconfdir=<path>
-
- */
+    3. C:/
+    4. Directory above where the executable is located
+    5. getenv(DEFAULT_HOME_ENV)
+    6. --defaults-extra-file=<path> (run-time option)
+*/
 
-static void init_default_directories()
+static void init_default_directories_win()
 {
-  const char *env, **ptr= default_directories;
+  bzero(default_directories, sizeof(default_directories));
 
-#ifdef __WIN__
-  *ptr++= "C:/";
+  if (my_get_system_windows_directory(shared_system_dir,
+                                      sizeof(shared_system_dir)))
+    ADD_DIRECTORY(&shared_system_dir);
 
   if (GetWindowsDirectory(system_dir,sizeof(system_dir)))
-    *ptr++= (char*)&system_dir;
-  if (my_get_system_windows_directory(shared_system_dir,
-                                      sizeof(shared_system_dir)) &&
-      strcmp(system_dir, shared_system_dir))
-    *ptr++= (char *)&shared_system_dir;
+    ADD_DIRECTORY(&system_dir);
+
+  ADD_DIRECTORY("C:/");
 
-#elif defined(__NETWARE__)
-  *ptr++= "sys:/etc/";
-#else
-#if defined(__EMX__) || defined(OS2)
-  if ((env= getenv("ETC")))
-    *ptr++= env;
-#endif
-  *ptr++= "/etc/";
-#endif
-  if ((env= getenv(STRINGIFY_ARG(DEFAULT_HOME_ENV))))
-    *ptr++= env;
-  *ptr++= "";			/* Place for defaults_extra_file */
-#if !defined(__WIN__) && !defined(__NETWARE__)
-  *ptr++= "~/";;
-#elif defined(__WIN__)
   if (GetModuleFileName(NULL, config_dir, sizeof(config_dir)))
   {
     char *last= NULL, *end= strend(config_dir);
@@ -1043,12 +1037,84 @@ static void init_default_directories()
         last= end;
       }
     }
-    *ptr++= (char *)&config_dir;
+    ADD_DIRECTORY(&config_dir);
   }
-#endif
+
+  ADD_COMMON_DIRECTORIES();
+}
+
+static void (*init_default_directories)()= init_default_directories_win;
+
+#elif defined(__NETWARE__)
+
+/**
+  Initialize default directories for Novell Netware
+
+  @details
+    1. sys:/etc/
+    2. getenv(DEFAULT_HOME_ENV)
+    3. --defaults-extra-file=<path> (run-time option)
+*/
+
+static void init_default_directories_netware()
+{
+  bzero(default_directories, sizeof(default_directories));
+  ADD_DIRECTORY("sys:/etc/");
+  ADD_COMMON_DIRECTORIES();
+}
+
+static void (*init_default_directories)()= init_default_directories_netware;
+
+#elif defined(__EMX__) || defined(OS2)
+
+/**
+  Initialize default directories for OS/2
+
+  @details
+    1. /etc/
+    2. getenv(ETC)
+    3. getenv(DEFAULT_HOME_ENV)
+    4. --defaults-extra-file=<path> (run-time option)
+*/
+
+static void init_default_directories_os2()
+{
+  const char *env;
+
+  bzero(default_directories, sizeof(default_directories));
+  ADD_DIRECTORY("/etc/");
+  if ((env= getenv("ETC")))
+    ADD_DIRECTORY(env);
+  ADD_COMMON_DIRECTORIES();
+}
+
+static void (*init_default_directories)()= init_default_directories_os2;
+
+#else
+
+/**
+  Initialize default directories for Unix
+
+  @details
+    1. /etc/
+    2. --sysconfdir=<path> (compile-time option)
+    3. getenv(DEFAULT_HOME_ENV)
+    4. --defaults-extra-file=<path> (run-time option)
+    5. "~/"
+*/
+
+static void init_default_directories_unix()
+{
+  bzero(default_directories, sizeof(default_directories));
+  ADD_DIRECTORY("/etc/");
 #ifdef DEFAULT_SYSCONFDIR
   if (DEFAULT_SYSCONFDIR != "")
-    *ptr++= DEFAULT_SYSCONFDIR;
+    ADD_DIRECTORY(DEFAULT_SYSCONFDIR);
 #endif
-  *ptr= 0;			/* end marker */
+  ADD_COMMON_DIRECTORIES();
+  ADD_DIRECTORY("~/");
 }
+
+static void (*init_default_directories)()= init_default_directories_unix;
+
+#endif