error: Do not define _cairo_error twice

cairo-perf-trace uses cairo-hash.c, which calls _cairo_error.

Instead of redefining it in cairo-perf-trace.c it can be abstracted in
a separate source which is directly included in the build of
cairo-perf-trace.

This avoids visibility issues when compiling cairo-perf-trace with a
statically linked cairo library on architectures which do not support
hidden visibility (example: win32).

perf/Makefile.am

@@ -81,6 +81,7 @@ libcairoperf_la_SOURCES = \
 
 cairo_perf_trace_SOURCES =		\
 	cairo-perf-trace.c		\
+	../src/cairo-error.c		\
 	../src/cairo-hash.c
 if CAIRO_HAS_WIN32_SURFACE
 cairo_perf_trace_SOURCES += cairo-perf-win32.c

perf/cairo-perf-trace.c

@@ -884,9 +884,3 @@ main (int   argc,
 
     return 0;
 }
-
-cairo_status_t
-_cairo_error (cairo_status_t status)
-{
-    return status;
-}

src/Makefile.sources

@@ -123,6 +123,7 @@ cairo_sources = \
 	cairo-composite-rectangles.c \
 	cairo-debug.c \
 	cairo-device.c \
+	cairo-error.c \
 	cairo-fixed.c \
 	cairo-font-face.c \
 	cairo-font-face-twin.c \

src/cairo-error.c

@@ -0,0 +1,69 @@
+/* -*- Mode: c; c-basic-offset: 4; indent-tabs-mode: t; tab-width: 8; -*- */
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2002 University of Southern California
+ * Copyright © 2005 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is University of Southern
+ * California.
+ *
+ * Contributor(s):
+ *	Carl D. Worth <cworth@cworth.org>
+ */
+
+#include "cairoint.h"
+#include "cairo-private.h"
+
+#include "cairo-error-private.h"
+#include <assert.h>
+
+/**
+ * _cairo_error:
+ * @status: a status value indicating an error, (eg. not
+ * %CAIRO_STATUS_SUCCESS)
+ *
+ * Checks that status is an error status, but does nothing else.
+ *
+ * All assignments of an error status to any user-visible object
+ * within the cairo application should result in a call to
+ * _cairo_error().
+ *
+ * The purpose of this function is to allow the user to set a
+ * breakpoint in _cairo_error() to generate a stack trace for when the
+ * user causes cairo to detect an error.
+ *
+ * Return value: the error status.
+ **/
+cairo_status_t
+_cairo_error (cairo_status_t status)
+{
+    CAIRO_ENSURE_UNIQUE;
+    assert (_cairo_status_is_error (status));
+
+    return status;
+}

src/cairo.c

@@ -153,32 +153,6 @@ static const cairo_t _cairo_nil__null_pointer = {
 };
 #include <assert.h>
 
-/**
- * _cairo_error:
- * @status: a status value indicating an error, (eg. not
- * %CAIRO_STATUS_SUCCESS)
- *
- * Checks that status is an error status, but does nothing else.
- *
- * All assignments of an error status to any user-visible object
- * within the cairo application should result in a call to
- * _cairo_error().
- *
- * The purpose of this function is to allow the user to set a
- * breakpoint in _cairo_error() to generate a stack trace for when the
- * user causes cairo to detect an error.
- *
- * Return value: the error status.
- **/
-cairo_status_t
-_cairo_error (cairo_status_t status)
-{
-    CAIRO_ENSURE_UNIQUE;
-    assert (_cairo_status_is_error (status));
-
-    return status;
-}
-
 /**
  * _cairo_set_error:
  * @cr: a cairo context