[Libguestfs] [PATCH 1/1] Switch from YAJL to Jansson

Pino Toscano ptoscano at redhat.com
Thu Nov 23 13:23:52 UTC 2017


While YAJL mostly works fine, it did not see any active development in
the latest 3 years.  OTOH, Jansson is another JSON C implementation,
with a very liberal license, and a much nicer API.

Hence, switch all of libguestfs from YAJL to Jansson:
- configure checks, and buildsystem in general
- packages pulled in the appliance
- actual implementations
- contrib scripts
- documentation

This also makes use of the better APIs available (e.g. json_object_get,
json_array_foreach, and json_object_foreach).  This does not change the
API of our OCaml Yajl module.

The only behaviour change is that Jansson by default accepts only
objects and arrays as input (even though it has a flag to make it accept
anything).  Since this seems a good idea anyway, and as it is the RFC
behaviour, then change one of the yajl_tests checks accordingly.
---
 appliance/packagelist.in            |  13 ++--
 builder/Makefile.am                 |   4 +-
 builder/yajl-c.c                    |  66 ++++++++++-----------
 builder/yajl_tests.ml               |   4 +-
 contrib/p2v/aux-scripts/do-build.sh |   8 +--
 contrib/p2v/build-p2v-iso.sh        |   3 +-
 daemon/Makefile.am                  |   4 +-
 daemon/ldm.c                        | 115 ++++++++++++++++--------------------
 docs/guestfs-building.pod           |   2 +-
 lib/Makefile.am                     |   4 +-
 lib/info.c                          | 113 ++++++++++++++---------------------
 lib/qemu.c                          |  64 +++++++-------------
 m4/guestfs-libraries.m4             |   4 +-
 13 files changed, 170 insertions(+), 234 deletions(-)

diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index 9e5080029..78aedad0b 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -35,6 +35,7 @@ ifelse(REDHAT,1,
   hivex
   iproute
   iputils
+  jansson
   kernel
   libcap
   libldm
@@ -51,7 +52,6 @@ ifelse(REDHAT,1,
   systemd              dnl for /sbin/reboot and udevd
   vim-minimal
   xz
-  yajl
   yara
   zfs-fuse
 )
@@ -81,12 +81,12 @@ dnl iproute has been renamed to iproute2
   libc-bin
   libcap2
   libhivex0
+  libjansson4
   libpcre3
   libsystemd0
   libsystemd-id128-0
   libsystemd-journal0
   libtirpc1
-  libyajl2
   libyara3
   linux-image
   dnl syslinux 'suggests' mtools, but in reality it's a hard dependency:
@@ -115,6 +115,7 @@ ifelse(ARCHLINUX,1,
   hivex
   iproute2
   iputils
+  jansson
   libcap
   libtirpc
   linux
@@ -130,7 +131,6 @@ ifelse(ARCHLINUX,1,
   systemd
   vim
   xz
-  yajl
   yara
 )
 
@@ -152,9 +152,9 @@ ifelse(SUSE,1,
   iputils
   libcap2
   libhivex0
+  libjansson4
   libselinux1
   libtirpc3
-  libyajl2
   libyara3
   mkisofs
   ntfsprogs
@@ -176,6 +176,7 @@ ifelse(FRUGALWARE,1,
   hfsplus
   iproute2
   iputils
+  jansson
   kernel
   libcap
   libtirpc
@@ -187,7 +188,6 @@ ifelse(FRUGALWARE,1,
   systemd
   vim
   xz
-  yajl
   xfsprogs-acl
   xfsprogs-attr
   gptfdisk
@@ -208,9 +208,9 @@ ifelse(MAGEIA,1,
   iproute2
   iputils
   libcap
+  libjansson4
   libldm
   libtirpc
-  libyajl
   dnl syslinux uses mtools without depending on it
   mtools
   nilfs-utils
@@ -223,7 +223,6 @@ ifelse(MAGEIA,1,
   systemd /* for /sbin/reboot and udevd */
   vim-minimal
   xz
-  yajl
 )
 
 acl
diff --git a/builder/Makefile.am b/builder/Makefile.am
index 979726bff..7eeb9d85c 100644
--- a/builder/Makefile.am
+++ b/builder/Makefile.am
@@ -155,7 +155,7 @@ virt_builder_CFLAGS = \
 	$(LIBLZMA_CFLAGS) \
 	$(LIBTINFO_CFLAGS) \
 	$(LIBXML2_CFLAGS) \
-	$(YAJL_CFLAGS)
+	$(JANSSON_CFLAGS)
 
 BOBJECTS = $(SOURCES_ML:.ml=.cmo)
 XOBJECTS = $(BOBJECTS:.cmo=.cmx)
@@ -209,7 +209,7 @@ OCAMLCLIBS = \
 	$(LIBCRYPT_LIBS) \
 	$(LIBLZMA_LIBS) \
 	$(LIBXML2_LIBS) \
-	$(YAJL_LIBS) \
+	$(JANSSON_LIBS) \
 	$(LIBINTL) \
 	-lgnu
 
diff --git a/builder/yajl-c.c b/builder/yajl-c.c
index 3c2402e42..03fbced6e 100644
--- a/builder/yajl-c.c
+++ b/builder/yajl-c.c
@@ -23,24 +23,17 @@
 #include <caml/memory.h>
 #include <caml/mlvalues.h>
 
-#include <yajl/yajl_tree.h>
+#include <jansson.h>
 
 #include <stdio.h>
 #include <string.h>
 
-/* GCC can't work out that the YAJL_IS_<foo> test is sufficient to
- * ensure that YAJL_GET_<foo> later doesn't return NULL.
- */
-#if defined(__GNUC__) && __GNUC__ >= 6 /* gcc >= 6 */
-#pragma GCC diagnostic ignored "-Wnull-dereference"
-#endif
-
 #define Val_none (Val_int (0))
 
 value virt_builder_yajl_tree_parse (value stringv);
 
 static value
-convert_yajl_value (yajl_val val, int level)
+convert_json_t (json_t *val, int level)
 {
   CAMLparam0 ();
   CAMLlocal4 (rv, lv, v, sv);
@@ -48,46 +41,51 @@ convert_yajl_value (yajl_val val, int level)
   if (level > 20)
     caml_invalid_argument ("too many levels of object/array nesting");
 
-  if (YAJL_IS_OBJECT (val)) {
-    const size_t len = YAJL_GET_OBJECT(val)->len;
+  if (json_is_object (val)) {
+    const size_t len = json_object_size (val);
     size_t i;
+    const char *key;
+    json_t *jvalue;
     rv = caml_alloc (1, 3);
     lv = caml_alloc_tuple (len);
-    for (i = 0; i < len; ++i) {
+    i = 0;
+    json_object_foreach (val, key, jvalue) {
       v = caml_alloc_tuple (2);
-      sv = caml_copy_string (YAJL_GET_OBJECT(val)->keys[i]);
+      sv = caml_copy_string (key);
       Store_field (v, 0, sv);
-      sv = convert_yajl_value (YAJL_GET_OBJECT(val)->values[i], level + 1);
+      sv = convert_json_t (jvalue, level + 1);
       Store_field (v, 1, sv);
       Store_field (lv, i, v);
+      ++i;
     }
     Store_field (rv, 0, lv);
-  } else if (YAJL_IS_ARRAY (val)) {
-    const size_t len = YAJL_GET_ARRAY(val)->len;
+  } else if (json_is_array (val)) {
+    const size_t len = json_array_size (val);
     size_t i;
+    json_t *jvalue;
     rv = caml_alloc (1, 4);
     lv = caml_alloc_tuple (len);
-    for (i = 0; i < len; ++i) {
-      v = convert_yajl_value (YAJL_GET_ARRAY(val)->values[i], level + 1);
+    json_array_foreach (val, i, jvalue) {
+      v = convert_json_t (jvalue, level + 1);
       Store_field (lv, i, v);
     }
     Store_field (rv, 0, lv);
-  } else if (YAJL_IS_STRING (val)) {
+  } else if (json_is_string (val)) {
     rv = caml_alloc (1, 0);
-    v = caml_copy_string (YAJL_GET_STRING(val));
+    v = caml_copy_string (json_string_value (val));
     Store_field (rv, 0, v);
-  } else if (YAJL_IS_DOUBLE (val)) {
+  } else if (json_is_real (val)) {
     rv = caml_alloc (1, 2);
-    v = caml_copy_double (YAJL_GET_DOUBLE(val));
+    v = caml_copy_double (json_real_value (val));
     Store_field (rv, 0, v);
-  } else if (YAJL_IS_INTEGER (val)) {
+  } else if (json_is_integer (val)) {
     rv = caml_alloc (1, 1);
-    v = caml_copy_int64 (YAJL_GET_INTEGER(val));
+    v = caml_copy_int64 (json_integer_value (val));
     Store_field (rv, 0, v);
-  } else if (YAJL_IS_TRUE (val)) {
+  } else if (json_is_true (val)) {
     rv = caml_alloc (1, 5);
     Store_field (rv, 0, Val_true);
-  } else if (YAJL_IS_FALSE (val)) {
+  } else if (json_is_false (val)) {
     rv = caml_alloc (1, 5);
     Store_field (rv, 0, Val_false);
   } else
@@ -101,21 +99,21 @@ virt_builder_yajl_tree_parse (value stringv)
 {
   CAMLparam1 (stringv);
   CAMLlocal1 (rv);
-  yajl_val tree;
-  char error_buf[256];
+  json_t *tree;
+  json_error_t err;
 
-  tree = yajl_tree_parse (String_val (stringv), error_buf, sizeof error_buf);
+  tree = json_loads (String_val (stringv), 0, &err);
   if (tree == NULL) {
-    char buf[256 + sizeof error_buf];
-    if (strlen (error_buf) > 0)
-      snprintf (buf, sizeof buf, "JSON parse error: %s", error_buf);
+    char buf[256 + JSON_ERROR_TEXT_LENGTH];
+    if (strlen (err.text) > 0)
+      snprintf (buf, sizeof buf, "JSON parse error: %s", err.text);
     else
       snprintf (buf, sizeof buf, "unknown JSON parse error");
     caml_invalid_argument (buf);
   }
 
-  rv = convert_yajl_value (tree, 1);
-  yajl_tree_free (tree);
+  rv = convert_json_t (tree, 1);
+  json_decref (tree);
 
   CAMLreturn (rv);
 }
diff --git a/builder/yajl_tests.ml b/builder/yajl_tests.ml
index f5a44f2fa..3d780d4f1 100644
--- a/builder/yajl_tests.ml
+++ b/builder/yajl_tests.ml
@@ -82,6 +82,7 @@ let test_tree_parse_invalid ctx =
   assert_raises_invalid_argument "";
   assert_raises_invalid_argument "invalid";
   assert_raises_invalid_argument ":5";
+  assert_raises_invalid_argument "\"foo\"";
 
   (* Nested objects/arrays. *)
   let str = "[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]" in
@@ -93,9 +94,6 @@ let test_tree_parse_basic ctx =
   let value = yajl_tree_parse "{}" in
   assert_is_object value;
 
-  let value = yajl_tree_parse "\"foo\"" in
-  assert_is_string "foo" value;
-
   let value = yajl_tree_parse "[]" in
   assert_is_array value
 
diff --git a/contrib/p2v/aux-scripts/do-build.sh b/contrib/p2v/aux-scripts/do-build.sh
index 5edb53d0e..dd6424bb4 100644
--- a/contrib/p2v/aux-scripts/do-build.sh
+++ b/contrib/p2v/aux-scripts/do-build.sh
@@ -53,8 +53,8 @@ case $osversion in
         # This just forces configure to ignore these missing dependencies.
         export LIBTINFO_CFLAGS=-D_GNU_SOURCE
         export LIBTINFO_LIBS=-lncurses
-        export YAJL_CFLAGS=-D_GNU_SOURCE
-        export YAJL_LIBS=-lyajl
+        export JANSSON_CFLAGS=-D_GNU_SOURCE
+        export JANSSON_LIBS=-ljansson
         # Remove some unsupported flags that the configure script hard codes.
         sed -i -e 's/-fno-strict-overflow//' configure
         sed -i -e 's/-Wno-strict-overflow//' configure
@@ -66,8 +66,8 @@ case $osversion in
         # This just forces configure to ignore these missing dependencies.
         export LIBTINFO_CFLAGS=-D_GNU_SOURCE
         export LIBTINFO_LIBS=-lncurses
-        export YAJL_CFLAGS=-D_GNU_SOURCE
-        export YAJL_LIBS=-lyajl
+        export JANSSON_CFLAGS=-D_GNU_SOURCE
+        export JANSSON_LIBS=-ljansson
         ;;
 esac
 
diff --git a/contrib/p2v/build-p2v-iso.sh b/contrib/p2v/build-p2v-iso.sh
index c80a1b134..ae25cebc8 100755
--- a/contrib/p2v/build-p2v-iso.sh
+++ b/contrib/p2v/build-p2v-iso.sh
@@ -86,7 +86,6 @@ done
 # Various hacks for different versions of RHEL.
 if=virtio
 netdev=virtio-net-pci
-pkgs="$pkgs,yajl-devel"
 declare -a epel
 case $osversion in
     rhel-5.*|centos-5.*)
@@ -105,10 +104,12 @@ case $osversion in
     rhel-6.*|centos-6.*)
         epel[0]="--run-command"
         epel[1]="yum install -y --nogpgcheck https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm"
+        pkgs="$pkgs,jansson-devel"
         ;;
     rhel-7.*|centos-7.*)
         epel[0]="--run-command"
         epel[1]="yum install -y --nogpgcheck https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm"
+        pkgs="$pkgs,jansson-devel"
         ;;
 esac
 
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index 27630d2bc..cc8154c88 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -201,7 +201,7 @@ guestfsd_LDADD = \
 	camldaemon.o \
 	$(ACL_LIBS) \
 	$(CAP_LIBS) \
-	$(YAJL_LIBS) \
+	$(JANSSON_LIBS) \
 	$(SELINUX_LIBS) \
 	$(AUGEAS_LIBS) \
 	$(HIVEX_LIBS) \
@@ -239,7 +239,7 @@ guestfsd_CFLAGS = \
 	$(AUGEAS_CFLAGS) \
 	$(HIVEX_CFLAGS) \
 	$(SD_JOURNAL_CFLAGS) \
-	$(YAJL_CFLAGS) \
+	$(JANSSON_CFLAGS) \
 	$(PCRE_CFLAGS)
 
 # Parts of the daemon are written in OCaml.  These are linked into a
diff --git a/daemon/ldm.c b/daemon/ldm.c
index 2f4d2aef3..be4fb9701 100644
--- a/daemon/ldm.c
+++ b/daemon/ldm.c
@@ -25,19 +25,12 @@
 #include <sys/stat.h>
 #include <string.h>
 
-#include <yajl/yajl_tree.h>
+#include <jansson.h>
 
 #include "daemon.h"
 #include "actions.h"
 #include "optgroups.h"
 
-/* GCC can't work out that the YAJL_IS_<foo> test is sufficient to
- * ensure that YAJL_GET_<foo> later doesn't return NULL.
- */
-#if defined(__GNUC__) && GUESTFS_GCC_VERSION >= 60000 /* gcc >= 6 */
-#pragma GCC diagnostic ignored "-Wnull-dereference"
-#endif
-
 int
 optgroup_ldm_available (void)
 {
@@ -72,44 +65,42 @@ do_ldmtool_remove_all (void)
   return 0;
 }
 
-static yajl_val
+static json_t *
 parse_json (const char *json, const char *func)
 {
-  yajl_val tree;
-  char parse_error[1024];
+  json_t *tree;
+  json_error_t err;
 
   if (verbose)
     fprintf (stderr, "%s: parsing json: %s\n", func, json);
 
-  tree = yajl_tree_parse (json, parse_error, sizeof parse_error);
+  tree = json_loads (json, 0, &err);
   if (tree == NULL) {
     reply_with_error ("parse error: %s",
-                      strlen (parse_error) ? parse_error : "unknown error");
+                      strlen (err.text) ? err.text : "unknown error");
     return NULL;
   }
 
-  /* Caller should free this by doing 'yajl_tree_free (tree);'. */
+  /* Caller should free this by doing 'json_decref (tree);'. */
   return tree;
 }
 
 #define TYPE_ERROR ((char **) -1)
 
 static char **
-json_value_to_string_list (yajl_val node)
+json_value_to_string_list (json_t *node)
 {
   CLEANUP_FREE_STRINGSBUF DECLARE_STRINGSBUF (strs);
-  yajl_val n;
-  size_t i, len;
+  json_t *n;
+  size_t i;
 
-  if (! YAJL_IS_ARRAY (node))
+  if (!json_is_array (node))
     return TYPE_ERROR;
 
-  len = YAJL_GET_ARRAY (node)->len;
-  for (i = 0; i < len; ++i) {
-    n = YAJL_GET_ARRAY (node)->values[i];
-    if (! YAJL_IS_STRING (n))
+  json_array_foreach (node, i, n) {
+    if (!json_is_string (n))
       return TYPE_ERROR;
-    if (add_string (&strs, YAJL_GET_STRING (n)) == -1)
+    if (add_string (&strs, json_string_value (n)) == -1)
       return NULL;
   }
   if (end_stringsbuf (&strs) == -1)
@@ -123,14 +114,14 @@ parse_json_get_string_list (const char *json,
                             const char *func, const char *cmd)
 {
   char **ret;
-  yajl_val tree = NULL;
+  json_t *tree = NULL;
 
   tree = parse_json (json, func);
   if (tree == NULL)
     return NULL;
 
   ret = json_value_to_string_list (tree);
-  yajl_tree_free (tree);
+  json_decref (tree);
   if (ret == TYPE_ERROR) {
     reply_with_error ("output of '%s' was not a JSON array of strings", cmd);
     return NULL;
@@ -144,43 +135,40 @@ static char *
 parse_json_get_object_string (const char *json, const char *key, int flags,
                               const char *func, const char *cmd)
 {
-  char *str, *ret;
-  yajl_val tree = NULL, node;
-  size_t i, len;
+  const char *str;
+  char *ret;
+  json_t *tree = NULL, *node;
 
   tree = parse_json (json, func);
   if (tree == NULL)
     return NULL;
 
-  if (! YAJL_IS_OBJECT (tree))
+  if (!json_is_object (tree))
+    goto bad_type;
+
+  node = json_object_get (tree, key);
+  if (node == NULL)
     goto bad_type;
 
-  len = YAJL_GET_OBJECT (tree)->len;
-  for (i = 0; i < len; ++i) {
-    if (STREQ (YAJL_GET_OBJECT (tree)->keys[i], key)) {
-      node = YAJL_GET_OBJECT (tree)->values[i];
-
-      if ((flags & GET_STRING_NULL_TO_EMPTY) && YAJL_IS_NULL (node))
-        ret = strdup ("");
-      else {
-        str = YAJL_GET_STRING (node);
-        if (str == NULL)
-          goto bad_type;
-        ret = strdup (str);
-      }
-      if (ret == NULL)
-        reply_with_perror ("strdup");
-
-      yajl_tree_free (tree);
-
-      return ret;
-    }
+  if ((flags & GET_STRING_NULL_TO_EMPTY) && json_is_null (node))
+    ret = strdup ("");
+  else {
+    str = json_string_value (node);
+    if (str == NULL)
+      goto bad_type;
+    ret = strndup (str, json_string_length (node));
   }
+  if (ret == NULL)
+    reply_with_perror ("strdup");
+
+  json_decref (tree);
+
+  return ret;
 
  bad_type:
   reply_with_error ("output of '%s' was not a JSON object "
                     "containing a key '%s' of type string", cmd, key);
-  yajl_tree_free (tree);
+  json_decref (tree);
   return NULL;
 }
 
@@ -189,33 +177,30 @@ parse_json_get_object_string_list (const char *json, const char *key,
                                    const char *func, const char *cmd)
 {
   char **ret;
-  yajl_val tree, node;
-  size_t i, len;
+  json_t *tree, *node;
 
   tree = parse_json (json, func);
   if (tree == NULL)
     return NULL;
 
-  if (! YAJL_IS_OBJECT (tree))
+  if (!json_is_object (tree))
     goto bad_type;
 
-  len = YAJL_GET_OBJECT (tree)->len;
-  for (i = 0; i < len; ++i) {
-    if (STREQ (YAJL_GET_OBJECT (tree)->keys[i], key)) {
-      node = YAJL_GET_OBJECT (tree)->values[i];
-      ret = json_value_to_string_list (node);
-      if (ret == TYPE_ERROR)
-        goto bad_type;
-      yajl_tree_free (tree);
-      return ret;
-    }
-  }
+  node = json_object_get (tree, key);
+  if (node == NULL)
+    goto bad_type;
+
+  ret = json_value_to_string_list (node);
+  if (ret == TYPE_ERROR)
+    goto bad_type;
+  json_decref (tree);
+  return ret;
 
  bad_type:
   reply_with_error ("output of '%s' was not a JSON object "
                     "containing a key '%s' of type array of strings",
                     cmd, key);
-  yajl_tree_free (tree);
+  json_decref (tree);
   return NULL;
 }
 
diff --git a/docs/guestfs-building.pod b/docs/guestfs-building.pod
index a75983b83..e1b54b967 100644
--- a/docs/guestfs-building.pod
+++ b/docs/guestfs-building.pod
@@ -169,7 +169,7 @@ I<Required>.
 
 I<Required>.
 
-=item yajl E<ge> 2.0.4
+=item Jansson
 
 I<Required>.
 
diff --git a/lib/Makefile.am b/lib/Makefile.am
index a1d8ee70e..6e97a4844 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -141,7 +141,7 @@ libguestfs_la_CFLAGS = \
 	$(PCRE_CFLAGS) \
 	$(LIBVIRT_CFLAGS) \
 	$(LIBXML2_CFLAGS) \
-	$(YAJL_CFLAGS)
+	$(JANSSON_CFLAGS)
 
 libguestfs_la_LIBADD = \
 	../common/errnostring/liberrnostring.la \
@@ -152,7 +152,7 @@ libguestfs_la_LIBADD = \
 	$(PCRE_LIBS) \
 	$(LIBVIRT_LIBS) $(LIBXML2_LIBS) \
 	$(SELINUX_LIBS) \
-	$(YAJL_LIBS) \
+	$(JANSSON_LIBS) \
 	../gnulib/lib/libgnu.la \
 	$(GETADDRINFO_LIB) \
 	$(HOSTENT_LIB) \
diff --git a/lib/info.c b/lib/info.c
index f7378adfd..ada4cf03c 100644
--- a/lib/info.c
+++ b/lib/info.c
@@ -38,53 +38,46 @@
 #include <sys/resource.h>
 #endif
 
-#include <yajl/yajl_tree.h>
+#include <jansson.h>
 
 #include "guestfs.h"
 #include "guestfs-internal.h"
 #include "guestfs-internal-actions.h"
 
 #ifdef HAVE_ATTRIBUTE_CLEANUP
-#define CLEANUP_YAJL_TREE_FREE __attribute__((cleanup(cleanup_yajl_tree_free)))
+#define CLEANUP_JSON_T_DECREF __attribute__((cleanup(cleanup_json_t_decref)))
 
 static void
-cleanup_yajl_tree_free (void *ptr)
+cleanup_json_t_decref (void *ptr)
 {
-  yajl_tree_free (* (yajl_val *) ptr);
+  json_decref (* (json_t **) ptr);
 }
 
 #else
-#define CLEANUP_YAJL_TREE_FREE
+#define CLEANUP_JSON_T_DECREF
 #endif
 
-static yajl_val get_json_output (guestfs_h *g, const char *filename);
+static json_t *get_json_output (guestfs_h *g, const char *filename);
 static void set_child_rlimits (struct command *);
 
 char *
 guestfs_impl_disk_format (guestfs_h *g, const char *filename)
 {
-  size_t i, len;
-  CLEANUP_YAJL_TREE_FREE yajl_val tree = get_json_output (g, filename);
+  CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
+  json_t *node;
 
   if (tree == NULL)
     return NULL;
 
-  if (! YAJL_IS_OBJECT (tree))
+  if (!json_is_object (tree))
     goto bad_type;
 
-  len = YAJL_GET_OBJECT(tree)->len;
-  for (i = 0; i < len; ++i) {
-    if (STREQ (YAJL_GET_OBJECT(tree)->keys[i], "format")) {
-      const char *str;
-      yajl_val node = YAJL_GET_OBJECT(tree)->values[i];
-      if (YAJL_IS_NULL (node))
-        goto bad_type;
-      str = YAJL_GET_STRING (node);
-      if (str == NULL)
-        goto bad_type;
-      return safe_strdup (g, str); /* caller frees */
-    }
-  }
+  node = json_object_get (tree, "format");
+  if (!json_is_string (node))
+    goto bad_type;
+
+  return safe_strndup (g, json_string_value (node),
+                          json_string_length (node)); /* caller frees */
 
  bad_type:
   error (g, _("qemu-img info: JSON output did not contain ‘format’ key"));
@@ -94,30 +87,20 @@ guestfs_impl_disk_format (guestfs_h *g, const char *filename)
 int64_t
 guestfs_impl_disk_virtual_size (guestfs_h *g, const char *filename)
 {
-  size_t i, len;
-  CLEANUP_YAJL_TREE_FREE yajl_val tree = get_json_output (g, filename);
+  CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
+  json_t *node;
 
   if (tree == NULL)
     return -1;
 
-  if (! YAJL_IS_OBJECT (tree))
+  if (!json_is_object (tree))
     goto bad_type;
 
-  len = YAJL_GET_OBJECT(tree)->len;
-  for (i = 0; i < len; ++i) {
-    if (STREQ (YAJL_GET_OBJECT(tree)->keys[i], "virtual-size")) {
-      yajl_val node = YAJL_GET_OBJECT(tree)->values[i];
-      if (YAJL_IS_NULL (node))
-        goto bad_type;
-      if (! YAJL_IS_NUMBER (node))
-        goto bad_type;
-      if (! YAJL_IS_INTEGER (node)) {
-        error (g, _("qemu-img info: ‘virtual-size’ is not representable as a 64 bit integer"));
-        return -1;
-      }
-      return YAJL_GET_INTEGER (node);
-    }
-  }
+  node = json_object_get (tree, "virtual-size");
+  if (!json_is_integer (node))
+    goto bad_type;
+
+  return json_integer_value (node);
 
  bad_type:
   error (g, _("qemu-img info: JSON output did not contain ‘virtual-size’ key"));
@@ -127,29 +110,25 @@ guestfs_impl_disk_virtual_size (guestfs_h *g, const char *filename)
 int
 guestfs_impl_disk_has_backing_file (guestfs_h *g, const char *filename)
 {
-  size_t i, len;
-  CLEANUP_YAJL_TREE_FREE yajl_val tree = get_json_output (g, filename);
+  CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
+  json_t *node;
 
   if (tree == NULL)
     return -1;
 
-  if (! YAJL_IS_OBJECT (tree))
+  if (!json_is_object (tree))
     goto bad_type;
 
-  len = YAJL_GET_OBJECT(tree)->len;
-  for (i = 0; i < len; ++i) {
-    if (STREQ (YAJL_GET_OBJECT(tree)->keys[i], "backing-filename")) {
-      yajl_val node = YAJL_GET_OBJECT(tree)->values[i];
-      /* Work on the assumption that if this field is null, it means
-       * no backing file, rather than being an error.
-       */
-      if (YAJL_IS_NULL (node))
-        return 0;
-      return 1;
-    }
-  }
+  node = json_object_get (tree, "backing-filename");
+  if (node == NULL)
+    return 0; /* no backing-filename key means no backing file */
 
-  return 0; /* no backing-filename key means no backing file */
+  /* Work on the assumption that if this field is null, it means
+   * no backing file, rather than being an error.
+   */
+  if (json_is_null (node))
+    return 0;
+  return 1;
 
  bad_type:
   error (g, _("qemu-img info: JSON output was not an object"));
@@ -162,13 +141,13 @@ guestfs_impl_disk_has_backing_file (guestfs_h *g, const char *filename)
 static void parse_json (guestfs_h *g, void *treevp, const char *input, size_t len);
 #define PARSE_JSON_NO_OUTPUT ((void *) -1)
 
-static yajl_val
+static json_t *
 get_json_output (guestfs_h *g, const char *filename)
 {
   CLEANUP_CMD_CLOSE struct command *cmd = guestfs_int_new_command (g);
   int fd, r;
   char fdpath[64];
-  yajl_val tree = NULL;
+  json_t *tree = NULL;
   struct stat statbuf;
 
   fd = open (filename, O_RDONLY /* NB: !O_CLOEXEC */);
@@ -217,16 +196,15 @@ get_json_output (guestfs_h *g, const char *filename)
     return NULL;
   }
 
-  return tree;          /* caller must call yajl_tree_free (tree) */
+  return tree;          /* caller must call json_decref (tree) */
 }
 
 /* Parse the JSON document printed by qemu-img info --output json. */
 static void
 parse_json (guestfs_h *g, void *treevp, const char *input, size_t len)
 {
-  yajl_val *tree_ret = treevp;
-  CLEANUP_FREE char *input_copy = NULL;
-  char parse_error[256];
+  json_t **tree_ret = treevp;
+  json_error_t err;
 
   assert (*tree_ret == NULL);
 
@@ -239,15 +217,12 @@ parse_json (guestfs_h *g, void *treevp, const char *input, size_t len)
     return;
   }
 
-  /* 'input' is not \0-terminated; we have to make it so. */
-  input_copy = safe_strndup (g, input, len);
-
-  debug (g, "%s: qemu-img info JSON output:\n%s\n", __func__, input_copy);
+  debug (g, "%s: qemu-img info JSON output:\n%.*s\n", __func__, (int) len, input);
 
-  *tree_ret = yajl_tree_parse (input_copy, parse_error, sizeof parse_error);
+  *tree_ret = json_loadb (input, len, 0, &err);
   if (*tree_ret == NULL) {
-    if (strlen (parse_error) > 0)
-      error (g, _("qemu-img info: JSON parse error: %s"), parse_error);
+    if (strlen (err.text) > 0)
+      error (g, _("qemu-img info: JSON parse error: %s"), err.text);
     else
       error (g, _("qemu-img info: unknown JSON parse error"));
   }
diff --git a/lib/qemu.c b/lib/qemu.c
index d27664733..b21897a29 100644
--- a/lib/qemu.c
+++ b/lib/qemu.c
@@ -37,7 +37,7 @@
 
 #include <libxml/uri.h>
 
-#include <yajl/yajl_tree.h>
+#include <jansson.h>
 
 #include "full-write.h"
 #include "ignore-value.h"
@@ -57,7 +57,7 @@ struct qemu_data {
 
   /* The following fields are derived from the fields above. */
   struct version qemu_version;  /* Parsed qemu version number. */
-  yajl_val qmp_schema_tree;     /* qmp_schema parsed into a JSON tree */
+  json_t *qmp_schema_tree;      /* qmp_schema parsed into a JSON tree */
 };
 
 static char *cache_filename (guestfs_h *g, const char *cachedir, const struct stat *, const char *suffix);
@@ -73,7 +73,7 @@ static int write_cache_qmp_schema (guestfs_h *g, const struct qemu_data *data, c
 static int read_cache_qemu_stat (guestfs_h *g, struct qemu_data *data, const char *filename);
 static int write_cache_qemu_stat (guestfs_h *g, const struct qemu_data *data, const char *filename);
 static void parse_qemu_version (guestfs_h *g, const char *, struct version *qemu_version);
-static void parse_json (guestfs_h *g, const char *, yajl_val *);
+static void parse_json (guestfs_h *g, const char *, json_t **);
 static void read_all (guestfs_h *g, void *retv, const char *buf, size_t len);
 static int generic_read_cache (guestfs_h *g, const char *filename, char **strp);
 static int generic_write_cache (guestfs_h *g, const char *filename, const char *str);
@@ -405,17 +405,17 @@ parse_qemu_version (guestfs_h *g, const char *qemu_help,
  * is not possible.
  */
 static void
-parse_json (guestfs_h *g, const char *json, yajl_val *treep)
+parse_json (guestfs_h *g, const char *json, json_t **treep)
 {
-  char parse_error[256] = "";
+  json_error_t err;
 
   if (!json)
     return;
 
-  *treep = yajl_tree_parse (json, parse_error, sizeof parse_error);
+  *treep = json_loads (json, 0, &err);
   if (*treep == NULL) {
-    if (strlen (parse_error) > 0)
-      debug (g, "QMP parse error: %s (ignored)", parse_error);
+    if (strlen (err.text) > 0)
+      debug (g, "QMP parse error: %s (ignored)", err.text);
     else
       debug (g, "QMP unknown parse error (ignored)");
   }
@@ -580,17 +580,6 @@ guestfs_int_qemu_supports_device (guestfs_h *g,
   return strstr (data->qemu_devices, device_name) != NULL;
 }
 
-/* GCC can't work out that the YAJL_IS_<foo> test is sufficient to
- * ensure that YAJL_GET_<foo> later doesn't return NULL.
- */
-#pragma GCC diagnostic push
-#if defined(__GNUC__) && __GNUC__ >= 6 /* gcc >= 6 */
-#pragma GCC diagnostic ignored "-Wnull-dereference"
-#endif
-#if defined(__GNUC__) && GUESTFS_GCC_VERSION >= 40800 /* gcc >= 4.8.0 */
-#pragma GCC diagnostic ignored "-Wnonnull"
-#endif
-
 /**
  * Test if the qemu binary uses mandatory file locking, added in
  * QEMU >= 2.10 (but sometimes disabled).
@@ -599,11 +588,7 @@ int
 guestfs_int_qemu_mandatory_locking (guestfs_h *g,
                                     const struct qemu_data *data)
 {
-  const char *return_path[] = { "return", NULL };
-  const char *meta_type_path[] = { "meta-type", NULL };
-  const char *members_path[] = { "members", NULL };
-  const char *name_path[] = { "name", NULL };
-  yajl_val schema, v, meta_type, members, m, name;
+  json_t *schema, *v, *meta_type, *members, *m, *name;
   size_t i, j;
 
   /* If there's no QMP schema, fall back to checking the version. */
@@ -616,27 +601,24 @@ guestfs_int_qemu_mandatory_locking (guestfs_h *g,
    * Extract the schema from the wrapper.  Note the returned ‘schema’
    * will be an array.
    */
-  schema = yajl_tree_get (data->qmp_schema_tree, return_path, yajl_t_array);
-  if (schema == NULL)
+  schema = json_object_get (data->qmp_schema_tree, "return");
+  if (!json_is_array (schema))
     goto fallback;
-  assert (YAJL_IS_ARRAY(schema));
 
   /* Now look for any member of the array which has:
    * { "meta-type": "object",
    *   "members": [ ... { "name": "locking", ... } ... ] ... }
    */
-  for (i = 0; i < YAJL_GET_ARRAY(schema)->len; ++i) {
-    v = YAJL_GET_ARRAY(schema)->values[i];
-    meta_type = yajl_tree_get (v, meta_type_path, yajl_t_string);
-    if (meta_type && YAJL_IS_STRING (meta_type) &&
-        STREQ (YAJL_GET_STRING (meta_type), "object")) {
-      members = yajl_tree_get (v, members_path, yajl_t_array);
-      if (members) {
-        for (j = 0; j < YAJL_GET_ARRAY(members)->len; ++j) {
-          m = YAJL_GET_ARRAY(members)->values[j];
-          name = yajl_tree_get (m, name_path, yajl_t_string);
-          if (name && YAJL_IS_STRING (name) &&
-              STREQ (YAJL_GET_STRING (name), "locking"))
+  json_array_foreach (schema, i, v) {
+    meta_type = json_object_get (v, "meta-type");
+    if (json_is_string (meta_type) &&
+        STREQ (json_string_value (meta_type), "object")) {
+      members = json_object_get (v, "members");
+      if (json_is_array (members)) {
+        json_array_foreach (members, j, m) {
+          name = json_object_get (v, "name");
+          if (json_is_string (name) &&
+              STREQ (json_string_value (name), "locking"))
             return 1;
         }
       }
@@ -646,8 +628,6 @@ guestfs_int_qemu_mandatory_locking (guestfs_h *g,
   return 0;
 }
 
-#pragma GCC diagnostic pop
-
 /**
  * Escape a qemu parameter.
  *
@@ -995,7 +975,7 @@ guestfs_int_free_qemu_data (struct qemu_data *data)
     free (data->qemu_help);
     free (data->qemu_devices);
     free (data->qmp_schema);
-    yajl_tree_free (data->qmp_schema_tree);
+    json_decref (data->qmp_schema_tree);
     free (data);
   }
 }
diff --git a/m4/guestfs-libraries.m4 b/m4/guestfs-libraries.m4
index 963f725bd..58a05ef1e 100644
--- a/m4/guestfs-libraries.m4
+++ b/m4/guestfs-libraries.m4
@@ -284,8 +284,8 @@ LIBS="$LIBS $LIBXML2_LIBS"
 AC_CHECK_FUNCS([xmlBufferDetach])
 LIBS="$old_LIBS"
 
-dnl Check for yajl JSON library (required).
-PKG_CHECK_MODULES([YAJL], [yajl >= 2.0.4])
+dnl Check for Jansson JSON library (required).
+PKG_CHECK_MODULES([JANSSON], [jansson])
 
 dnl Check for C++ (optional, we just use this to test the header works).
 AC_PROG_CXX
-- 
2.13.6




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