Remove use of __environ

It has apparently never worked. Fixes #2988

configure.ac

@@ -675,30 +675,6 @@ else
   AC_MSG_RESULT(no)
 fi
 
-# Check for __environ symbol
-AC_MSG_CHECKING([for __environ symbol])
-AC_TRY_LINK(
-  [
-    #include <unistd.h>
-  ],
-  [
-    extern char **__environ;
-    char **tmp = __environ;
-    exit(tmp!=0);
-  ],
-  have___environ=yes,
-  have___environ=no
-)
-if test "$have___environ" = yes; then
-  AC_MSG_RESULT(yes)
-  AC_DEFINE(
-    [HAVE___ENVIRON],
-    [1],
-    [Define to 1 if the __environ symbol is exported.]
-  )
-else
-  AC_MSG_RESULT(no)
-fi
 
 # Check for sys_errlist
 AC_MSG_CHECKING([for sys_errlist array])

osx/config.h

@@ -206,9 +206,6 @@
 /* Define to 1 if the _sys_errs array is available. */
 /* #undef HAVE__SYS__ERRS */
 
-/* Define to 1 if the __environ symbol is exported. */
-/* #undef HAVE___ENVIRON */
-
 /* Define to 1 to disable ncurses macros that conflict with the STL */
 #define NCURSES_NOMACROS 1
 

src/env.cpp

@@ -45,8 +45,6 @@
 
 /// At init, we read all the environment variables from this array.
 extern char **environ;
-/// This should be the same thing as \c environ, but it is possible only one of the two work...
-extern char **__environ;
 
 bool g_log_forks = false;
 bool g_use_posix_spawn = false;  // will usually be set to true
@@ -311,7 +309,7 @@ void env_init(const struct config_paths_t *paths /* or NULL */) {
     // Import environment variables. Walk backwards so that the first one out of any duplicates wins
     // (#2784).
     wcstring key, val;
-    const char *const *envp = (environ ? environ : __environ);
+    const char *const *envp = environ;
     size_t i = 0;
     while (envp && envp[i]) {
         i++;

src/fallback.cpp

@@ -46,12 +46,6 @@
 #include "fallback.h"  // IWYU pragma: keep
 #include "util.h"  // IWYU pragma: keep
 
-#ifndef HAVE___ENVIRON
-
-char **__environ = 0;
-
-#endif
-
 #ifdef TPUTS_KLUDGE
 
 int tputs(const char *str, int affcnt, int (*fish_putc)(tputs_arg_t))