lib: Expose errno through new API guestfs_last_errno.

If either the daemon sends back an errno, or a system call
fails in the library, save the errno in the handle and then
make it available to callers through the guestfs_last_errno
function.

3 files changed, 78 insertions, 2 deletions

diff --git a/generator/generator_c.ml b/generator/generator_c.ml
index 513bc1da..c1b2e632 100644
--- a/generator/generator_c.ml
+++ b/generator/generator_c.ml
@@ -438,6 +438,7 @@ and generate_client_actions () =
 #include \"guestfs-internal.h\"
 #include \"guestfs-internal-actions.h\"
 #include \"guestfs_protocol.h\"
+#include \"errnostring.h\"
 
 /* Check the return message from a call for validity. */
 static int
@@ -802,7 +803,16 @@ check_state (guestfs_h *g, const char *caller)
       pr "\n";
 
       pr "  if (hdr.status == GUESTFS_STATUS_ERROR) {\n";
-      pr "    error (g, \"%%s: %%s\", \"%s\", err.error_message);\n" shortname;
+      pr "    int errnum = 0;\n";
+      pr "    if (err.errno_string[0] != '\\0')\n";
+      pr "      errnum = guestfs___string_to_errno (err.errno_string);\n";
+      pr "    if (errnum <= 0)\n";
+      pr "      error (g, \"%%s: %%s\", \"%s\", err.error_message);\n"
+        shortname;
+      pr "    else\n";
+      pr "      guestfs_error_errno (g, errnum, \"%%s: %%s\", \"%s\",\n"
+        shortname;
+      pr "                           err.error_message);\n";
       pr "    free (err.error_message);\n";
       pr "    free (err.errno_string);\n";
       pr "    guestfs___end_busy (g);\n";
@@ -995,6 +1005,7 @@ and generate_linker_script () =
     "guestfs_get_error_handler";
     "guestfs_get_out_of_memory_handler";
     "guestfs_get_private";
+    "guestfs_last_errno";
     "guestfs_last_error";
     "guestfs_set_close_callback";
     "guestfs_set_error_handler";
diff --git a/generator/generator_errnostring.ml b/generator/generator_errnostring.ml
index d0a5734f..a0249892 100644
--- a/generator/generator_errnostring.ml
+++ b/generator/generator_errnostring.ml
@@ -224,7 +224,11 @@ extern const char *guestfs___errno_to_string (int errnum);
  * system, EINVAL is returned (all POSIX-conforming systems must
  * support EINVAL).
  */
-//extern int guestfs___string_to_errno (const char *errnostr);
+extern int guestfs___string_to_errno (const char *errnostr);
+
+/* Private structure and function used by the perfect hash implementation. */
+struct errnostring_entry { char *name; int errnum; };
+extern const struct errnostring_entry *guestfs___string_to_errno_lookup (register const char *str, register unsigned int len);
 
 #endif /* GUESTFS_ERRNOSTRING_H_ */
 "
@@ -236,6 +240,7 @@ let generate_errnostring_c () =
 #include <config.h>
 
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 
 #include \"errnostring.h\"
@@ -270,4 +275,63 @@ guestfs___errno_to_string (int errnum)
     return errno_to_string[errnum];
 }
 
+int
+guestfs___string_to_errno (const char *errnostr)
+{
+  const struct errnostring_entry *v =
+    guestfs___string_to_errno_lookup (errnostr, strlen (errnostr));
+  if (v /* not necessary to check v->name != NULL here */)
+    return v->errnum;
+  else
+    return EINVAL;
+}
 "
+
+let generate_errnostring_gperf () =
+  generate_header CStyle LGPLv2plus;
+
+  pr "\
+%%language=ANSI-C
+%%define lookup-function-name guestfs___string_to_errno_lookup
+%%readonly-tables
+%%null-strings
+
+%%{
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include \"errnostring.h\"
+
+";
+
+  (* Some of these errnos might not exist on the target platform, but
+   * we are going to include E_ macros directly in the C output of
+   * gperf.  To avoid this causing errors, we include macros to define
+   * unknown errors as EINVAL (see specification of
+   * guestfs___string_to_errno above).  Note this only affects the
+   * single output file containing gperf-generated code.
+   *)
+  List.iter (
+    fun e ->
+      pr "#ifndef %s\n" e;
+      pr "#define %s EINVAL\n" e;
+      pr "#endif\n";
+  ) errnos;
+
+  pr "\
+
+%%}
+
+struct errnostring_entry;
+
+%%%%
+";
+
+  List.iter (
+    fun e ->
+      pr "%s, %s\n" e e
+  ) errnos
diff --git a/generator/generator_main.ml b/generator/generator_main.ml
index 1aa15d0f..2d4b2412 100644
--- a/generator/generator_main.ml
+++ b/generator/generator_main.ml
@@ -81,6 +81,7 @@ Run it from the top source directory using the command
   output_to "src/guestfs-structs.pod" generate_structs_pod;
   output_to "src/guestfs-actions.pod" generate_actions_pod;
   output_to "src/guestfs-availability.pod" generate_availability_pod;
+  output_to "src/errnostring_gperf.gperf" generate_errnostring_gperf;
   output_to "src/errnostring.c" generate_errnostring_c;
   output_to "src/errnostring.h" generate_errnostring_h;
   output_to "src/MAX_PROC_NR" generate_max_proc_nr;