utils: Fix error messages for external commands that fail (RHBZ#921040).

This adds a common utility function (guestfs___exit_status_to_string)
and a common error function (guestfs___external_command_failed), and
uses them all over the library and tools when converting exit status
in error messages etc.

fish/man.c

@@ -52,7 +52,12 @@ run_man (const char *cmd, size_t argc, char *argv[])
   if (r != 0)
     return -1;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    fprintf (stderr, _("the external 'man' program failed\n"));
+    char status_string[80];
+
+    fprintf (stderr, "%s\n",
+             guestfs___exit_status_to_string (r, "man",
+                                              status_string,
+                                              sizeof status_string));
     return -1;
   }
 

fuse/test-guestunmount-fd.c

@@ -35,8 +35,6 @@
 #include "guestfs.h"
 #include "guestfs-internal-frontend.h"
 
-static void display_exit_status (int status, FILE *fp);
-
 int
 main (int argc, char *argv[])
 {
@@ -82,9 +80,12 @@ main (int argc, char *argv[])
     exit (EXIT_FAILURE);
   }
   if (r != 0) {
-    fprintf (stderr, "%s: test failed: guestunmount unexpectedly ", argv[0]);
-    display_exit_status (status, stderr);
-    fputc ('\n', stderr);
+    char status_string[80];
+
+    fprintf (stderr, "%s: test failed: %s\n", argv[0],
+             guestfs___exit_status_to_string (r, "guestunmount",
+                                              status_string,
+                                              sizeof status_string));
     exit (EXIT_FAILURE);
   }
 
@@ -100,27 +101,15 @@ main (int argc, char *argv[])
     exit (EXIT_FAILURE);
   }
   if (!WIFEXITED (status) || WEXITSTATUS (status) != 2) {
-    fprintf (stderr, "%s: test failed: guestunmount didn't return status code 2; instead it ", argv[0]);
-    display_exit_status (status, stderr);
-    fputc ('\n', stderr);
+    char status_string[80];
+
+    fprintf (stderr, "%s: test failed: guestunmount didn't return status code 2; %s\n",
+             argv[0],
+             guestfs___exit_status_to_string (status, "guestunmount",
+                                              status_string,
+                                              sizeof status_string));
     exit (EXIT_FAILURE);
   }
 
   exit (EXIT_SUCCESS);
 }
-
-static void
-display_exit_status (int status, FILE *fp)
-{
-  if (WIFEXITED (status))
-    fprintf (fp, "exited with status code %d", WEXITSTATUS (status));
-  else if (WIFSIGNALED (status)) {
-    fprintf (fp, "exited on signal %d", WTERMSIG (status));
-    if (WCOREDUMP (status))
-      fprintf (fp, " and dumped core");
-  }
-  else if (WIFSTOPPED (status))
-    fprintf (fp, "stopped on signal %d", WSTOPSIG (status));
-  else
-    fprintf (fp, "<< unknown status %d >>", status);
-}

src/appliance.c

@@ -689,7 +689,7 @@ run_supermin_helper (guestfs_h *g, const char *supermin_path,
   if (r == -1)
     return -1;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("external command failed, see earlier error messages"));
+    guestfs___external_command_failed (g, r, SUPERMIN_HELPER, NULL);
     return -1;
   }
 

src/command.c

@@ -366,6 +366,7 @@ run_command (struct command *cmd)
   int i, fd, max_fd, r;
   int errorfd[2] = { -1, -1 };
   int outfd[2] = { -1, -1 };
+  char status_string[80];
 
   /* Set up a pipe to capture command output and send it to the error log. */
   if (cmd->capture_errors) {
@@ -470,16 +471,10 @@ run_command (struct command *cmd)
     }
     if (WIFEXITED (r))
       _exit (WEXITSTATUS (r));
-    if (WIFSIGNALED (r)) {
-      fprintf (stderr, "%s: received signal %d\n", cmd->string.str,
-               WTERMSIG (r));
-      _exit (EXIT_FAILURE);
-    }
-    if (WIFSTOPPED (r)) {
-      fprintf (stderr, "%s: stopped by signal %d\n", cmd->string.str,
-               WSTOPSIG (r));
-      _exit (EXIT_FAILURE);
-    }
+    fprintf (stderr, "%s\n",
+             guestfs___exit_status_to_string (r, cmd->string.str,
+                                              status_string,
+                                              sizeof status_string));
     _exit (EXIT_FAILURE);
 
   case COMMAND_STYLE_NOT_SELECTED:

src/dbdump.c

@@ -82,7 +82,7 @@ guestfs___read_db_dump (guestfs_h *g,
   if (r == -1)
     return -1;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("%s: command failed"), DB_DUMP);
+    guestfs___external_command_failed (g, r, DB_DUMP, NULL);
     return -1;
   }
   if (data.state != reading_finished) {

src/errors.c

@@ -304,3 +304,36 @@ guestfs___unexpected_close_error (guestfs_h *g)
 "See http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs\n"
 "for information about how to debug libguestfs and report bugs."));
 }
+
+/* External command failed. */
+void
+guestfs___external_command_failed (guestfs_h *g, int status,
+                                   const char *cmd_name, const char *extra)
+{
+  size_t len = 80 + strlen (cmd_name);
+  char status_string[len];
+
+  guestfs___exit_status_to_string (status, cmd_name, status_string, len);
+
+  if (g->verbose) {
+    if (!extra)
+      error (g, _("%s, see debug messages above"), status_string);
+    else
+      error (g, _("%s: %s: %s, see debug messages above"),
+             cmd_name, extra, status_string);
+  }
+  else {
+    if (!extra)
+      error (g, _(
+"%s.\n"
+"To see full error messages you may need to enable debugging.\n"
+"See http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs"),
+             status_string);
+    else
+      error (g, _(
+"%s: %s: %s.\n"
+"To see full error messages you may need to enable debugging.\n"
+"See http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs"),
+             cmd_name, extra, status_string);
+  }
+}

src/filearch.c

@@ -181,8 +181,10 @@ cpio_arch (guestfs_h *g, const char *file, const char *path)
   }
 
   r = guestfs___cmd_run (cmd);
-  if (r == -1 || !WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("cpio command failed (status 0x%x)"), r);
+  if (r == -1)
+    goto out;
+  if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
+    guestfs___external_command_failed (g, r, "cpio", path);
     goto out;
   }
 

src/guestfs-internal-frontend.h

@@ -91,6 +91,7 @@ extern char *guestfs___safe_asprintf (guestfs_h *g, const char *fs, ...)
 /* utils.c */
 extern void guestfs___free_string_list (char **);
 extern size_t guestfs___count_strings (char *const *);
+extern char *guestfs___exit_status_to_string (int status, const char *cmd_name, char *buffer, size_t buflen);
 
 /* These functions are used internally by the CLEANUP_* macros.
  * Don't call them directly.

src/guestfs-internal.h

@@ -508,6 +508,7 @@ extern void guestfs___print_BufferOut (FILE *out, const char *buf, size_t buf_si
 
 extern void guestfs___launch_failed_error (guestfs_h *g);
 extern void guestfs___unexpected_close_error (guestfs_h *g);
+extern void guestfs___external_command_failed (guestfs_h *g, int status, const char *cmd_name, const char *extra);
 
 /* actions-support.c */
 struct trace_buffer {

src/info.c

@@ -246,7 +246,7 @@ get_json_output (guestfs_h *g, const char *filename)
   if (r == -1)
     return NULL;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("qemu-img info: %s: child process failed"), filename);
+    guestfs___external_command_failed (g, r, "qemu-img info", filename);
     return NULL;
   }
 
@@ -508,7 +508,7 @@ old_parser_run_qemu_img_info (guestfs_h *g, const char *filename,
   if (r == -1)
     return -1;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("qemu-img: %s: child process failed"), filename);
+    guestfs___external_command_failed (g, r, "qemu-img info", filename);
     return -1;
   }
 

src/launch-appliance.c

@@ -785,7 +785,10 @@ test_qemu (guestfs_h *g)
   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."));
+  if (r == -1)
+    return -1;
+
+  guestfs___external_command_failed (g, r, g->qemu, NULL);
   return -1;
 }
 
@@ -995,7 +998,7 @@ static int
 shutdown_appliance (guestfs_h *g, int check_for_errors)
 {
   int ret = 0;
-  int status, sig;
+  int status;
 
   /* Signal qemu to shutdown cleanly, and kill the recovery process. */
   if (g->app.pid > 0) {
@@ -1010,18 +1013,8 @@ shutdown_appliance (guestfs_h *g, int check_for_errors)
       perrorf (g, "waitpid (qemu)");
       ret = -1;
     }
-    else if (WIFEXITED (status) && WEXITSTATUS (status) != 0) {
-      error (g, "qemu failed (status %d)", WEXITSTATUS (status));
-      ret = -1;
-    }
-    else if (WIFSIGNALED (status)) {
-      sig = WTERMSIG (status);
-      error (g, "qemu terminated by signal %d (%s)", sig, strsignal (sig));
-      ret = -1;
-    }
-    else if (WIFSTOPPED (status)) {
-      sig = WSTOPSIG (status);
-      error (g, "qemu stopped by signal %d (%s)", sig, strsignal (sig));
+    else if (!WIFEXITED (status) || WEXITSTATUS (status) != 0) {
+      guestfs___external_command_failed (g, status, g->qemu, NULL);
       ret = -1;
     }
   }

src/launch-libvirt.c

@@ -1427,7 +1427,7 @@ make_qcow2_overlay (guestfs_h *g, const char *path, const char *format,
   if (r == -1)
     goto error;
   if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    error (g, _("qemu-img create: could not create snapshot over %s"), path);
+    guestfs___external_command_failed (g, r, "qemu-img create", path);
     goto error;
   }
 

src/lpj.c

@@ -142,8 +142,15 @@ read_lpj_common (guestfs_h *g, const char *func, struct command *cmd)
   guestfs___cmd_set_stdout_callback (cmd, read_all, &buf,
                                      CMD_STDOUT_FLAG_WHOLE_BUFFER);
   r = guestfs___cmd_run (cmd);
-  if (r == -1 || !WIFEXITED (r) || WEXITSTATUS (r) != 0) {
-    debug (g, "%s: external command failed with code %d", func, r);
+  if (r == -1)
+    return -1;
+  if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
+    char status_string[80];
+
+    debug (g, "%s: %s", func,
+           guestfs___exit_status_to_string (r, "external command",
+                                            status_string,
+                                            sizeof status_string));
     return -1;
   }
 

src/utils.c

@@ -20,8 +20,12 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 #include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <libintl.h>
 
 #include "guestfs.h"
 #include "guestfs-internal-frontend.h"
@@ -49,3 +53,34 @@ guestfs___count_strings (char *const *argv)
 
   return r;
 }
+
+/* Translate a wait/system exit status into a printable string.  The
+ * string must be freed by the caller.
+ */
+char *
+guestfs___exit_status_to_string (int status, const char *cmd_name,
+                                 char *buffer, size_t buflen)
+{
+  if (WIFEXITED (status)) {
+    if (WEXITSTATUS (status) == 0)
+      snprintf (buffer, buflen, _("%s exited successfully"),
+                cmd_name);
+    else
+      snprintf (buffer, buflen, _("%s exited with error status %d"),
+                cmd_name, WEXITSTATUS (status));
+  }
+  else if (WIFSIGNALED (status)) {
+    snprintf (buffer, buflen, _("%s killed by signal %d (%s)"),
+              cmd_name, WTERMSIG (status), strsignal (WTERMSIG (status)));
+  }
+  else if (WIFSTOPPED (status)) {
+    snprintf (buffer, buflen, _("%s stopped by signal %d (%s)"),
+              cmd_name, WSTOPSIG (status), strsignal (WSTOPSIG (status)));
+  }
+  else {
+    snprintf (buffer, buflen, _("%s exited for an unknown reason (status %d)"),
+              cmd_name, status);
+  }
+
+  return buffer;
+}

tests/mount-local/test-parallel-mount-local.c

@@ -258,20 +258,14 @@ start_thread (void *statevp)
       perror ("waitpid");
       goto error;
     }
-    if (WIFEXITED (status)) {
-      if (WEXITSTATUS (status) != 0) {
-        fprintf (stderr, "%s: test exited with non-zero status %d\n",
-                 state->mp, WEXITSTATUS (status));
+    if (!WIFEXITED (status) || WEXITSTATUS (status) != 0) {
+      char status_string[80];
+
+      fprintf (stderr, "%s: %s\n", state->mp,
+               guestfs___exit_status_to_string (status, "test",
+                                                status_string,
+                                                sizeof status_string));
         goto error;
-      }
-    } else if (WIFSIGNALED (status)) {
-      fprintf (stderr, "%s: subprocess killed by signal %d\n",
-               state->mp, WTERMSIG (status));
-      goto error;
-    } else if (WIFSTOPPED (status)) {
-      fprintf (stderr, "%s: subprocess stopped by signal %d\n",
-               state->mp, WSTOPSIG (status));
-      goto error;
     }
 
     if (r == -1) /* guestfs_mount_local_run above failed */