configure: Stop avoiding -Wformat-zero-length.

Debian likes to enable -Wformat-zero-length, even over our code trying to
disable it.  It isn't too hard to make our code warning-free against this
option, so this commit both stops disabling it and fixes the warnings.

The first fix is to change set_subprogram_name() to take a plain string
instead of a format string, and to adjust its few callers.  This fixes one
warning since one of those callers passed in an empty string.

The second fix is to remove a test for ovs_scan() against an empty string.
I couldn't find a way to avoid a warning for this test, and it isn't too
valuable in any case.

This allows us to drop filtering for -Wformat from the Debian rules file,
so this commit removes it.

Signed-off-by: Ben Pfaff <blp@nicira.com>

configure.ac

@@ -1,4 +1,4 @@
-# Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
+# Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -144,7 +144,6 @@ OVS_ENABLE_OPTION([-Wextra])
 OVS_ENABLE_OPTION([-Wno-sign-compare])
 OVS_ENABLE_OPTION([-Wpointer-arith])
 OVS_ENABLE_OPTION([-Wformat-security])
-OVS_ENABLE_OPTION([-Wno-format-zero-length])
 OVS_ENABLE_OPTION([-Wswitch-enum])
 OVS_ENABLE_OPTION([-Wunused-parameter])
 OVS_ENABLE_OPTION([-Wbad-function-cast])

debian/rules

@@ -35,13 +35,6 @@ endif
 buildflags := $(shell if dpkg-buildflags --export=configure >/dev/null 2>&1; \
 	              then dpkg-buildflags --export=configure; fi)
 
-# dpkg-buildflags tends to turn on -Wformat, which is admirable, but
-# the -Wformat-zero-length subset of that option triggers a couple of
-# false positives in Open vSwitch so turn it right back off again.
-# (We do this in configure.ac also, but the Debian buildflags override
-# those.)
-buildflags := $(patsubst -Wformat,-Wformat -Wno-format-zero-length,$(buildflags))
-
 configure: configure-stamp
 configure-stamp:
 	dh_testdir

lib/ovs-thread.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2013, 2014, 2015 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -332,7 +332,9 @@ ovsthread_wrapper(void *aux_)
 
     /* The order of the following calls is important, because
      * ovsrcu_quiesce_end() saves a copy of the thread name. */
-    set_subprogram_name("%s%u", aux.name, id);
+    char *subprogram_name = xasprintf("%s%u", aux.name, id);
+    set_subprogram_name(subprogram_name);
+    free(subprogram_name);
     ovsrcu_quiesce_end();
 
     return aux.start(aux.arg);

lib/util.c

@@ -500,24 +500,13 @@ get_subprogram_name(void)
     return name ? name : "";
 }
 
-/* Sets the formatted value of 'format' as the name of the currently running
+/* Sets 'subprogram_name' as the name of the currently running thread or
- * thread or process.  (This appears in log messages and may also be visible in
+ * process.  (This appears in log messages and may also be visible in system
- * system process listings and debuggers.) */
+ * process listings and debuggers.) */
 void
-set_subprogram_name(const char *format, ...)
+set_subprogram_name(const char *subprogram_name)
 {
-    char *pname;
+    char *pname = xstrdup(subprogram_name ? subprogram_name : program_name);
-
-    if (format) {
-        va_list args;
-
-        va_start(args, format);
-        pname = xvasprintf(format, args);
-        va_end(args);
-    } else {
-        pname = xstrdup(program_name);
-    }
-
     free(subprogram_name_set(pname));
 
 #if HAVE_GLIBC_PTHREAD_SETNAME_NP

lib/util.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -263,7 +263,7 @@ extern "C" {
         ovs_set_program_name(name, OVS_PACKAGE_VERSION)
 
 const char *get_subprogram_name(void);
-void set_subprogram_name(const char *format, ...) OVS_PRINTF_FORMAT(1, 2);
+    void set_subprogram_name(const char *);
 
 void ovs_print_version(uint8_t min_ofp, uint8_t max_ofp);
 

tests/test-util.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2012, 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -497,7 +497,6 @@ test_ovs_scan(struct ovs_cmdl_context *ctx OVS_UNUSED)
     long l, l2;
     int i, i2;
 
-    ovs_assert(ovs_scan("", ""));
     ovs_assert(ovs_scan("", " "));
     ovs_assert(ovs_scan(" ", " "));
     ovs_assert(ovs_scan("  ", " "));