daemon: Fix possible use-after-free.

This is essentially a backport of
<https://github.com/NixOS/nix/commit/f52b6c944e90b3e35925122779175705fdc02e12>
by Eelco Dolstra <eelco.dolstra@logicblox.com>.

The use-after-free bug would typically manifest when building with
GCC 5.1.

1 files changed, 5 insertions, 0 deletions

diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh
index ce2d77c19a..a70981877b 100644
--- a/nix/libutil/util.hh
+++ b/nix/libutil/util.hh
@@ -257,6 +257,11 @@ void killUser(uid_t uid);
 string runProgram(Path program, bool searchPath = false,
     const Strings & args = Strings());
 
+/* Convert a list of strings to a null-terminated vector of char
+   *'s. The result must not be accessed beyond the lifetime of the
+   list of strings. */
+std::vector<const char *> stringsToCharPtrs(const Strings & ss);
+
 /* Close all file descriptors except stdin, stdout, stderr, and those
    listed in the given set.  Good practice in child processes. */
 void closeMostFDs(const set<int> & exceptions);