Implement secure rc file saving.

First data is written to a temporary file, then if nothing
was wrong, this file is renamed to the final name.
This way the risk of corrupted rc file is greatly reduced.
The code is borrowed from ELinks (http://elinks.cz).

configure.in

@@ -24,7 +24,7 @@ AC_DEFINE_UNQUOTED(GQVIEW_HELPDIR, "$prefix/share/doc/geeqie-$VERSION", [Locatio
 AC_DEFINE_UNQUOTED(GQVIEW_HTMLDIR, "$prefix/share/doc/geeqie-$VERSION/html", [Location of html documentation])
 
 dnl checks for functions
-AC_CHECK_FUNCS(strverscmp)
+AC_CHECK_FUNCS(strverscmp access fsync fflush)
 
 dnl check for little cms (lcms, this test pulled from gimp)
 AC_ARG_WITH(lcms, [  --without-lcms          build without lcms support])

src/filelist.c

@@ -364,7 +364,7 @@ gint filter_file_class(const gchar *name, FileFormatClass file_class)
 	return FALSE;
 }
 
-void filter_write_list(FILE *f)
+void filter_write_list(SecureSaveInfo *ssi)
 {
 	GList *work;
 
@@ -377,8 +377,9 @@ void filter_write_list(FILE *f)
 		gchar *extensions = escquote_value(fe->extensions);
 		gchar *description = escquote_value(fe->description);
 
-		fprintf(f, "filter_ext: \"%s%s\" %s %s\n", (fe->enabled) ? "" : "#",
-			fe->key, extensions, description);
+		secure_fprintf(ssi, "filter_ext: \"%s%s\" %s %s\n",
+			       (fe->enabled) ? "" : "#",
+			       fe->key, extensions, description);
 		g_free(extensions);
 		g_free(description);
 		}
@@ -490,9 +491,9 @@ void sidecar_ext_parse(const gchar *text, gint quoted)
 	g_free(value);
 }
 
-void sidecar_ext_write(FILE *f)
+void sidecar_ext_write(SecureSaveInfo *ssi)
 {
-	fprintf(f, "\nsidecar_ext: \"%s\"\n", sidecar_ext_to_string());
+	secure_fprintf(ssi, "\nsidecar_ext: \"%s\"\n", sidecar_ext_to_string());
 }
 
 char *sidecar_ext_to_string()

src/filelist.h

@@ -37,11 +37,11 @@ GList *filter_to_list(const gchar *extensions);
 gint filter_name_exists(const gchar *name);
 gint filter_file_class(const gchar *name, FileFormatClass file_class);
 
-void filter_write_list(FILE *f);
+void filter_write_list(SecureSaveInfo *ssi);
 void filter_parse(const gchar *text);
 
 void sidecar_ext_parse(const gchar *text, gint quoted);
-void sidecar_ext_write(FILE *f);
+void sidecar_ext_write(SecureSaveInfo *ssi);
 char *sidecar_ext_to_string(); 
 void sidecar_ext_add_defaults();