Re: [Xen-devel] [PATCH v2 1/4] xen: indicate gcov in log messages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.09.16 at 14:47, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 06/09/16 13:41, Wei Liu wrote:
>> --- a/xen/drivers/char/console.c
>> +++ b/xen/drivers/char/console.c
>> @@ -735,10 +735,11 @@ void __init console_init_preirq(void)
>>      spin_lock(&console_lock);
>>      __putstr(xen_banner());
>>      spin_unlock(&console_lock);
>> -    printk("Xen version %d.%d%s (%s@%s) (%s) debug=%c %s\n",
>> +    printk("Xen version %d.%d%s (%s@%s) (%s) debug=%c gcov=%c %s\n",
> 
> Please instead use
> 
> printk("Xen version %d.%d%s (%s@%s) (%s) debug=%c"
> #ifdef CONFIG_GCOV
> " gcov=y"
> #endif
> " %s\n",
> 
> Enabling gcov will be extremely rare in the grand scheme of things, and
> this method causes zero overhead for the case where gcov is compiled
> out.  (Similarly elsewhere.)

How about instead of the kind of ugly #ifdef-ery above, instead of

+#ifdef CONFIG_GCOV
+#define gcov_build() 1
+#else
+#define gcov_build() 0
+#endif

we'd have

+#ifdef CONFIG_GCOV
+#define gcov_string "gcov=y"
+#else
+#define gcov_string ""
+#endif

(with the identifier name open for improvement), which can then be
embedded easily into any string literal?

Jan


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