From 249aae0c2ffa685008c03f5d06e05c2989b1ec99 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Thu, 16 Oct 2014 08:36:33 +0200
Subject: [PATCH] handle: Process empty LIBGUESTFS_* environment variables
 correctly (RHBZ#1153515).

Ignore an environment variable:

 - if an environment variable is an empty string, AND

 - if an empty string would have no meaning for that environment
   variable (eg. LIBGUESTFS_BACKEND can only take on certain values,
   and an empty string is not one of them).

Note that LIBGUESTFS_BACKEND_SETTINGS is meaningful as an empty
string, and for this case I have removed the STRNEQ (str, "") test.

Previously:

$ LIBGUESTFS_BACKEND="" guestfish -a /dev/null run
libguestfs: error: invalid backend:

After this commit:

$ LIBGUESTFS_BACKEND="" guestfish -a /dev/null run

(no error message is printed)
---
 src/handle.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/handle.c b/src/handle.c
index 0200528ae..141ba7de9 100644
--- a/src/handle.c
+++ b/src/handle.c
@@ -192,13 +192,13 @@ parse_environment (guestfs_h *g,
     guestfs_set_verbose (g, 1);
 
   str = do_getenv (data, "LIBGUESTFS_TMPDIR");
-  if (str) {
+  if (str && STRNEQ (str, "")) {
     if (guestfs_set_tmpdir (g, str) == -1)
       return -1;
   }
 
   str = do_getenv (data, "LIBGUESTFS_CACHEDIR");
-  if (str) {
+  if (str && STRNEQ (str, "")) {
     if (guestfs_set_cachedir (g, str) == -1)
       return -1;
   }
@@ -208,15 +208,15 @@ parse_environment (guestfs_h *g,
     return -1;
 
   str = do_getenv (data, "LIBGUESTFS_PATH");
-  if (str)
+  if (str && STRNEQ (str, ""))
     guestfs_set_path (g, str);
 
   str = do_getenv (data, "LIBGUESTFS_HV");
-  if (str)
+  if (str && STRNEQ (str, ""))
     guestfs_set_hv (g, str);
   else {
     str = do_getenv (data, "LIBGUESTFS_QEMU");
-    if (str)
+    if (str && STRNEQ (str, ""))
       guestfs_set_hv (g, str);
   }
 
@@ -225,7 +225,7 @@ parse_environment (guestfs_h *g,
     guestfs_set_append (g, str);
 
   str = do_getenv (data, "LIBGUESTFS_MEMSIZE");
-  if (str) {
+  if (str && STRNEQ (str, "")) {
     if (sscanf (str, "%d", &memsize) != 1) {
       error (g, _("non-numeric value for LIBGUESTFS_MEMSIZE"));
       return -1;
@@ -237,20 +237,20 @@ parse_environment (guestfs_h *g,
   }
 
   str = do_getenv (data, "LIBGUESTFS_BACKEND");
-  if (str) {
+  if (str && STRNEQ (str, "")) {
     if (guestfs_set_backend (g, str) == -1)
       return -1;
   }
   else {
     str = do_getenv (data, "LIBGUESTFS_ATTACH_METHOD");
-    if (str) {
+    if (str && STRNEQ (str, "")) {
       if (guestfs_set_backend (g, str) == -1)
         return -1;
     }
   }
 
   str = do_getenv (data, "LIBGUESTFS_BACKEND_SETTINGS");
-  if (str && STRNEQ (str, "")) {
+  if (str) {
     CLEANUP_FREE_STRING_LIST char **settings = guestfs___split_string (':', str);
 
     if (settings == NULL) {