lib: Fix memory leak and simplify command code.

Fix the following memory leak found by valgrind:

==13629== 498 (112 direct, 386 indirect) bytes in 1 blocks are definitely lost in loss record 99 of 110
==13629==    at 0x4A06B2F: calloc (vg_replace_malloc.c:593)
==13629==    by 0x4CA564E: guestfs_safe_calloc (alloc.c:71)
==13629==    by 0x4CA9B02: guestfs___new_command (command.c:143)
==13629==    by 0x4CA66E9: guestfs___build_appliance (appliance.c:690)
==13629==    by 0x4CBD1B9: launch_libvirt (launch-libvirt.c:188)
==13629==    by 0x402E7E: main (virt-filesystems.c:349)

Also adjust the command code in several places to make it simpler.  We
can almost always call guestfs___cmd_close right after
guestfs___cmd_run, avoiding any need to close the handle along error
paths.

Tested by running the test suite under valgrind.

6 files changed, 16 insertions, 38 deletions

diff --git a/src/appliance.c b/src/appliance.c
index 8a22064b..e7ba60df 100644
--- a/src/appliance.c
+++ b/src/appliance.c
@@ -286,12 +286,10 @@ calculate_supermin_checksum (guestfs_h *g, const char *supermin_path)
   guestfs___cmd_set_stdout_callback (cmd, read_checksum, checksum, 0);
 
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   /* Errors here are non-fatal, so we don't need to call error(). */
-  if (r == -1) {
-    guestfs___cmd_close (cmd);
+  if (r == -1)
     return NULL;
-  }
-  guestfs___cmd_close (cmd);
 
   debug (g, "checksum of existing appliance: %s", checksum);
 
@@ -707,6 +705,7 @@ run_supermin_helper (guestfs_h *g, const char *supermin_path,
   guestfs___cmd_add_arg_format (cmd, "%s/root", cachedir);
 
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     return -1;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
diff --git a/src/fuse.c b/src/fuse.c
index 76d008a1..ab544f7c 100644
--- a/src/fuse.c
+++ b/src/fuse.c
@@ -1052,7 +1052,7 @@ guestfs__umount_local (guestfs_h *g,
   size_t i, tries;
   char *localmountpoint;
   char *fusermount_log = NULL;
-  struct command *cmd = NULL;
+  struct command *cmd;
   int r;
   FILE *fp;
   char error_message[4096];
@@ -1095,7 +1095,6 @@ guestfs__umount_local (guestfs_h *g,
     guestfs___cmd_clear_capture_errors (cmd);
     r = guestfs___cmd_run (cmd);
     guestfs___cmd_close (cmd);
-    cmd = NULL;
     if (r == -1)
       goto out;
     if (WIFEXITED (r) && WEXITSTATUS (r) == EXIT_SUCCESS) {
@@ -1127,8 +1126,6 @@ guestfs__umount_local (guestfs_h *g,
   }
 
  out:
-  if (cmd)
-    guestfs___cmd_close (cmd);
   if (fusermount_log) {
     unlink (fusermount_log);
     free (fusermount_log);
diff --git a/src/info.c b/src/info.c
index 156c11fe..6df3aafa 100644
--- a/src/info.c
+++ b/src/info.c
@@ -168,7 +168,7 @@ run_qemu_img_info (guestfs_h *g, const char *filename,
 {
   char *abs_filename = NULL;
   char *safe_filename = NULL;
-  struct command *cmd = NULL;
+  struct command *cmd;
   int r;
 
   if (guestfs___lazy_make_tmpdir (g) == -1)
@@ -194,6 +194,7 @@ run_qemu_img_info (guestfs_h *g, const char *filename,
   guestfs___cmd_add_arg (cmd, safe_filename);
   guestfs___cmd_set_stdout_callback (cmd, fn, data, 0);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     goto error;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
@@ -201,15 +202,11 @@ run_qemu_img_info (guestfs_h *g, const char *filename,
     goto error;
   }
 
-  guestfs___cmd_close (cmd);
   free (safe_filename);
   free (abs_filename);
   return 0;
 
  error:
-  if (cmd)
-    guestfs___cmd_close (cmd);
-
   free (safe_filename);
   free (abs_filename);
 
diff --git a/src/inspect-icon.c b/src/inspect-icon.c
index 4831ab1b..4b7f43a2 100644
--- a/src/inspect-icon.c
+++ b/src/inspect-icon.c
@@ -364,7 +364,7 @@ icon_cirros (guestfs_h *g, struct inspect_fs *fs, size_t *size_r)
   char *type = NULL;
   char *local = NULL;
   char *pngfile = NULL;
-  struct command *cmd = NULL;
+  struct command *cmd;
   int r;
 
   r = guestfs_exists (g, CIRROS_LOGO);
@@ -392,6 +392,7 @@ icon_cirros (guestfs_h *g, struct inspect_fs *fs, size_t *size_r)
   guestfs___cmd_add_string_unquoted (cmd, " | " PNMTOPNG " > ");
   guestfs___cmd_add_string_quoted   (cmd, pngfile);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     goto out;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
@@ -407,8 +408,6 @@ icon_cirros (guestfs_h *g, struct inspect_fs *fs, size_t *size_r)
   free (pngfile);
   free (local);
   free (type);
-  if (cmd)
-    guestfs___cmd_close (cmd);
 
   return ret;
 }
@@ -438,7 +437,7 @@ icon_windows_xp (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
 {
   char *ret;
   char *pngfile = NULL;
-  struct command *cmd = NULL;
+  struct command *cmd;
   int r;
 
   pngfile = safe_asprintf (g, "%s/windows-xp-icon.png", g->tmpdir);
@@ -450,14 +449,12 @@ icon_windows_xp (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
                                      " | " BMPTOPNM " | " PNMTOPNG " > ");
   guestfs___cmd_add_string_quoted   (cmd, pngfile);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     goto error;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
     goto not_found;
 
-  guestfs___cmd_close (cmd);
-  cmd = NULL;
-
   if (read_whole_file (g, pngfile, &ret, size_r) == -1)
     goto error;
 
@@ -466,14 +463,10 @@ icon_windows_xp (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
   return ret;
 
  error:
-  if (cmd)
-    guestfs___cmd_close (cmd);
   free (pngfile);
   return NULL;
 
  not_found:
-  if (cmd)
-    guestfs___cmd_close (cmd);
   free (pngfile);
   return NOT_FOUND;
 }
@@ -484,7 +477,7 @@ icon_windows_7 (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
 {
   char *ret;
   char *pngfile = NULL;
-  struct command *cmd = NULL;
+  struct command *cmd;
   int r;
 
   pngfile = safe_asprintf (g, "%s/windows-7-icon.png", g->tmpdir);
@@ -498,14 +491,12 @@ icon_windows_7 (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
                                      PNMTOPNG " > ");
   guestfs___cmd_add_string_quoted   (cmd, pngfile);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     goto error;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0)
     goto not_found;
 
-  guestfs___cmd_close (cmd);
-  cmd = NULL;
-
   if (read_whole_file (g, pngfile, &ret, size_r) == -1)
     goto error;
 
@@ -514,14 +505,10 @@ icon_windows_7 (guestfs_h *g, struct inspect_fs *fs, const char *explorer,
   return ret;
 
  error:
-  if (cmd)
-    guestfs___cmd_close (cmd);
   free (pngfile);
   return NULL;
 
  not_found:
-  if (cmd)
-    guestfs___cmd_close (cmd);
   free (pngfile);
   return NOT_FOUND;
 }
diff --git a/src/launch-appliance.c b/src/launch-appliance.c
index 17e90d9e..8b2fda07 100644
--- a/src/launch-appliance.c
+++ b/src/launch-appliance.c
@@ -755,9 +755,9 @@ test_qemu (guestfs_h *g)
   guestfs___cmd_set_stdout_callback (cmd, read_all, &g->app.qemu_help,
                                      CMD_STDOUT_FLAG_WHOLE_BUFFER);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1 || !WIFEXITED (r) || WEXITSTATUS (r) != 0)
     goto error;
-  guestfs___cmd_close (cmd);
 
   cmd = guestfs___new_command (g);
   guestfs___cmd_add_arg (cmd, g->qemu);
@@ -766,9 +766,9 @@ test_qemu (guestfs_h *g)
   guestfs___cmd_set_stdout_callback (cmd, read_all, &g->app.qemu_version,
                                      CMD_STDOUT_FLAG_WHOLE_BUFFER);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1 || !WIFEXITED (r) || WEXITSTATUS (r) != 0)
     goto error;
-  guestfs___cmd_close (cmd);
 
   cmd = guestfs___new_command (g);
   guestfs___cmd_add_arg (cmd, g->qemu);
@@ -782,15 +782,14 @@ test_qemu (guestfs_h *g)
   guestfs___cmd_set_stdout_callback (cmd, read_all, &g->app.qemu_devices,
                                      CMD_STDOUT_FLAG_WHOLE_BUFFER);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1 || !WIFEXITED (r) || WEXITSTATUS (r) != 0)
     goto error;
-  guestfs___cmd_close (cmd);
 
   return 0;
 
  error:
   error (g, _("qemu command failed\nIf qemu is located on a non-standard path, try setting the LIBGUESTFS_QEMU\nenvironment variable.  There may also be errors printed above."));
-  guestfs___cmd_close (cmd);
   return -1;
 }
 
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index e4df2a6b..3ee4c0f8 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -1190,18 +1190,17 @@ make_qcow2_overlay (guestfs_h *g, const char *path, const char *format)
   }
   guestfs___cmd_add_arg (cmd, tmpfile);
   r = guestfs___cmd_run (cmd);
+  guestfs___cmd_close (cmd);
   if (r == -1)
     goto error;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
     error (g, _("qemu-img create: could not create snapshot over %s"), path);
     goto error;
   }
-  guestfs___cmd_close (cmd);
 
   return tmpfile;               /* caller frees */
 
  error:
-  guestfs___cmd_close (cmd);
   free (tmpfile);
 
   return NULL;