Hook for passing env pointer to main function

The new 'genode_envp' variable declared in '_main.cc' allows libc
plugins to supplying custom environment pointers to the main function.
This is needed by 3rd-party software such as GNU make, which expects the
environment pointer as third argument of the main function.

base/src/platform/_main.cc

@@ -31,7 +31,7 @@
 
 using namespace Genode;
 
-extern int main(int argc, char **argv);
+extern int main(int argc, char **argv, char **envp);
 extern void init_exception_handling();  /* implemented in base/cxx */
 
 enum { ATEXIT_SIZE = 256 };
@@ -212,6 +212,7 @@ static char *argv[1] = { argv0 };
  */
 char **genode_argv = argv;
 int    genode_argc = 1;
+char **genode_envp = 0;
 
 
 /**
@@ -250,7 +251,7 @@ extern "C" int _main()
 	/* now, it is save to call printf */
 
 	/* call real main function */
-	int ret = main(genode_argc, genode_argv);
+	int ret = main(genode_argc, genode_argv, genode_envp);
 
 	genode_exit(ret);
 

ports/src/lib/libc_noux/plugin.cc

@@ -1025,6 +1025,7 @@ namespace {
 /* external symbols provided by Genode's startup code */
 extern char **genode_argv;
 extern int    genode_argc;
+extern char **genode_envp;
 
 /* pointer to environment, provided by libc */
 extern char **environ;
@@ -1108,6 +1109,9 @@ void init_libc_noux(void)
 	/* register list of environment variables at libc 'environ' pointer */
 	environ = env_array;
 
+	/* define env pointer to be passed to main function (in '_main.cc') */
+	genode_envp = environ;
+
 	/* initialize noux libc plugin */
 	static Plugin noux_plugin;
 }