syntax: Remove PATH_MAX-sized buffers allocated on the stack.

On Linux PATH_MAX is 4096, but on some platforms it can be much larger
or even not defined (ie. unlimited).  Therefore using a PATH_MAX-sized
stack buffer is not a great idea for portable programs.

This change removes use of PATH_MAX-sized stack-allocated buffers.

This change only applies to the library and standalone programs.
Inside the daemon, memory allocation is much more complicated so I
have not changed those (yet).

Found by 'make syntax-check'.

cat/virt-filesystems.c

@@ -582,12 +582,14 @@ do_output_vgs (void)
     exit (EXIT_FAILURE);
 
   for (i = 0; i < vgs->len; ++i) {
-    char name[PATH_MAX];
+    char *name;
     char uuid[33];
     char **parents;
 
-    strcpy (name, "/dev/");
-    strcpy (&name[5], vgs->val[i].vg_name);
+    if (asprintf (&name, "/dev/%s", vgs->val[i].vg_name) == -1) {
+      perror ("asprintf");
+      exit (EXIT_FAILURE);
+    }
 
     memcpy (uuid, vgs->val[i].vg_uuid, 32);
     uuid[32] = '\0';
@@ -597,6 +599,7 @@ do_output_vgs (void)
     write_row (name, "vg",
                NULL, NULL, -1, (int64_t) vgs->val[i].vg_size, parents, uuid);
 
+    free (name);
     free_strings (parents);
   }
 

fish/copy.c

@@ -145,9 +145,10 @@ make_tar_from_local (const char *local)
   dup2 (fd[1], 1);
   close (fd[1]);
 
-  char buf[PATH_MAX];
+  size_t buf_len = strlen (local) + 1;
+  char buf[buf_len];
   const char *dirname, *basename;
-  if (split_path (buf, sizeof buf, local, &dirname, &basename) == -1)
+  if (split_path (buf, buf_len, local, &dirname, &basename) == -1)
     _exit (EXIT_FAILURE);
 
   tar_create (dirname, basename);
@@ -242,19 +243,26 @@ run_copy_out (const char *cmd, size_t argc, char *argv[])
       return -1;
     }
     if (r == 1) {               /* is file */
-      char buf[PATH_MAX];
+      size_t buf_len = strlen (remote) + 1;
+      char buf[buf_len];
       const char *basename;
-      if (split_path (buf, sizeof buf, remote, NULL, &basename) == -1) {
+      if (split_path (buf, buf_len, remote, NULL, &basename) == -1) {
         free (remote);
         return -1;
       }
 
-      char filename[PATH_MAX];
-      snprintf (filename, sizeof filename, "%s/%s", local, basename);
-      if (guestfs_download (g, remote, filename) == -1) {
+      char *filename;
+      if (asprintf (&filename, "%s/%s", local, basename) == -1) {
+        perror ("asprintf");
         free (remote);
         return -1;
       }
+      if (guestfs_download (g, remote, filename) == -1) {
+        free (remote);
+        free (filename);
+        return -1;
+      }
+      free (filename);
     }
     else {                      /* not a regular file */
       r = guestfs_is_dir (g, remote);
@@ -270,9 +278,10 @@ run_copy_out (const char *cmd, size_t argc, char *argv[])
         return -1;
       }
 
-      char buf[PATH_MAX];
+      size_t buf_len = strlen (remote) + 1;
+      char buf[buf_len];
       const char *basename;
-      if (split_path (buf, sizeof buf, remote, NULL, &basename) == -1) {
+      if (split_path (buf, buf_len, remote, NULL, &basename) == -1) {
         free (remote);
         return -1;
       }

src/launch-appliance.c

@@ -294,9 +294,10 @@ launch_appliance (guestfs_h *g, const char *arg)
           cachemode = ",cache=writeback";
       }
 
-      char buf2[PATH_MAX + 64];
+      size_t buf2_len = strlen (appliance) + 64;
+      char buf2[buf2_len];
       add_cmdline (g, "-drive");
-      snprintf (buf2, sizeof buf2, "file=%s,snapshot=on,id=appliance,if=%s%s",
+      snprintf (buf2, buf2_len, "file=%s,snapshot=on,id=appliance,if=%s%s",
                 appliance, virtio_scsi ? "none" : "virtio", cachemode);
       add_cmdline (g, buf2);
 

test-tool/test-tool.c

@@ -293,7 +293,7 @@ cleanup_wrapper (void)
 static void
 set_qemu (const char *path, int use_wrapper)
 {
-  char buffer[PATH_MAX];
+  char *buffer;
   struct stat statbuf;
   int fd;
   FILE *fp;
@@ -318,14 +318,19 @@ set_qemu (const char *path, int use_wrapper)
   }
 
   /* This should be a source directory, so check it. */
-  snprintf (buffer, sizeof buffer, "%s/pc-bios", path);
+  if (asprintf (&buffer, "%s/pc-bios", path) == -1) {
+    perror ("asprintf");
+    exit (EXIT_FAILURE);
+  }
   if (stat (buffer, &statbuf) == -1 ||
       !S_ISDIR (statbuf.st_mode)) {
     fprintf (stderr,
              _("%s: does not look like a qemu source directory\n"),
              path);
+    free (buffer);
     exit (EXIT_FAILURE);
   }
+  free (buffer);
 
   /* Make a wrapper script. */
   fd = mkstemp (qemuwrapper);