[libglnx] errors: Add glnx_throw() and tests

[Colin Walters <walters src gnome org>]

commit 602fdd93cb7a339c6b5749eee73df926429a5ab8
Author: Colin Walters <walters verbum org>
Date:   Tue Mar 21 11:19:16 2017 -0400

    errors: Add glnx_throw() and tests
    
    Following up to the previous commit, also shorten our use of
    `g_set_error (..., G_IO_ERROR_FAILED, ...)`. There's a lot of
    this in libostree at least.
    
    See also https://bugzilla.gnome.org/show_bug.cgi?id=774061

 Makefile-libglnx.am         |    6 +++-
 glnx-errors.h               |   25 +++++++++++++
 tests/test-libglnx-errors.c |   79 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 109 insertions(+), 1 deletions(-)
---
diff --git a/Makefile-libglnx.am b/Makefile-libglnx.am
index dfe6526..805a9d0 100644
--- a/Makefile-libglnx.am
+++ b/Makefile-libglnx.am
@@ -52,7 +52,7 @@ libglnx_la_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
 libglnx_la_LDFLAGS = -avoid-version -Bsymbolic-functions -export-symbols-regex "^glnx_" -no-undefined 
-export-dynamic 
 libglnx_la_LIBADD = $(libglnx_libs)
 
-libglnx_tests = test-libglnx-xattrs test-libglnx-fdio
+libglnx_tests = test-libglnx-xattrs test-libglnx-fdio test-libglnx-errors
 TESTS += $(libglnx_tests)
 
 check_PROGRAMS += $(libglnx_tests)
@@ -63,3 +63,7 @@ test_libglnx_xattrs_LDADD = $(libglnx_libs) libglnx.la
 test_libglnx_fdio_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-fdio.c
 test_libglnx_fdio_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
 test_libglnx_fdio_LDADD = $(libglnx_libs) libglnx.la
+
+test_libglnx_errors_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-errors.c
+test_libglnx_errors_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
+test_libglnx_errors_LDADD = $(libglnx_libs) libglnx.la
diff --git a/glnx-errors.h b/glnx-errors.h
index 7bf53d3..8f9cad8 100644
--- a/glnx-errors.h
+++ b/glnx-errors.h
@@ -25,6 +25,31 @@
 
 G_BEGIN_DECLS
 
+/* Set @error with G_IO_ERROR/G_IO_ERROR_FAILED.
+ *
+ * This function returns %FALSE so it can be used conveniently in a single
+ * statement:
+ *
+ * ``
+ *   if (strcmp (foo, "somevalue") != 0)
+ *     return glnx_throw (error, "key must be somevalue, not '%s'", foo);
+ * ```
+ */
+static inline gboolean G_GNUC_PRINTF (2,3)
+glnx_throw (GError **error, const char *fmt, ...)
+{
+  if (error == NULL)
+    return FALSE;
+
+  va_list args;
+  va_start (args, fmt);
+  GError *new = g_error_new_valist (G_IO_ERROR, G_IO_ERROR_FAILED, fmt, args);
+  va_end (args);
+  g_propagate_error (error, g_steal_pointer (&new));
+  return FALSE;
+}
+
+
 /* Set @error using the value of `g_strerror (errno)`.
  *
  * This function returns %FALSE so it can be used conveniently in a single
diff --git a/tests/test-libglnx-errors.c b/tests/test-libglnx-errors.c
new file mode 100644
index 0000000..8d109cd
--- /dev/null
+++ b/tests/test-libglnx-errors.c
@@ -0,0 +1,79 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+#include "libglnx.h"
+#include <glib.h>
+#include <stdlib.h>
+#include <gio/gio.h>
+#include <string.h>
+
+static void
+test_error_throw (void)
+{
+  g_autoptr(GError) error = NULL;
+
+  g_assert (!glnx_throw (&error, "foo: %s %d", "hello", 42));
+  g_assert_error (error, G_IO_ERROR, G_IO_ERROR_FAILED);
+  g_assert_cmpstr (error->message, ==, "foo: hello 42");
+}
+
+static void
+test_error_errno (void)
+{
+  g_autoptr(GError) error = NULL;
+  const char noent_path[] = "/enoent-this-should-not-exist";
+  int fd;
+
+  fd = open (noent_path, O_RDONLY);
+  if (fd < 0)
+    {
+      g_assert (!glnx_throw_errno (&error));
+      g_assert_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND);
+      g_clear_error (&error);
+    }
+  else
+    g_assert_cmpint (fd, ==, -1);
+
+  fd = open (noent_path, O_RDONLY);
+  if (fd < 0)
+    {
+      g_assert (!glnx_throw_errno_prefix (&error, "Failed to open %s", noent_path));
+      g_assert_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND);
+      g_assert (g_str_has_prefix (error->message, glnx_strjoina ("Failed to open ", noent_path)));
+      g_clear_error (&error);
+    }
+  else
+    g_assert_cmpint (fd, ==, -1);
+}
+
+int main (int argc, char **argv)
+{
+  int ret;
+
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/error-throw", test_error_throw);
+  g_test_add_func ("/error-errno", test_error_errno);
+
+  ret = g_test_run();
+
+  return ret;
+}