New function: replace-env.

Using this new function together with env, it's now possible
to save the set of environment variables, clobber it to a
specified set (possibly empty) and then restore it.

Useful for improved security in running child processes.

* lib.[ch] (chk_substrdup_utf8): New function.

* sysif.c (replace_env): New function.
(sysif_init): Register replace-env intrinsic.

* sysif.h (replace_env): Declared.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index f5b5ed42..25cfc6d1 100644
--- a/lib.h
+++ b/lib.h
@@ -735,6 +735,7 @@ wchar_t *chk_wrealloc(wchar_t *, size_t nwchar);
 wchar_t *chk_strdup(const wchar_t *str);
 wchar_t *chk_substrdup(const wchar_t *str, size_t off, size_t len);
 char *chk_strdup_utf8(const char *str);
+char *chk_substrdup_utf8(const char *str, size_t off, size_t len);
 unsigned char *chk_strdup_8bit(const wchar_t *str);
 mem_t *chk_copy_obj(mem_t *orig, size_t size);
 mem_t *chk_xalloc(ucnum m, ucnum n, val self);