Re: [PATCH v2] cxl/trace: Properly initialize cxl_poison region name

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 14 Mar 2024 14:05:00 -0700
Alison Schofield <alison.schofield@intel.com> wrote:

> > I'm still curious to why NULL didn't work. I guess it may never have as I
> > noticed there's nothing else doing that. There are cases that a variable
> > returns NULL and the __string() handles it. But I guess the compiler gets
> > confused if the NULL is a possible return to the condition in __string().  
> 
> Here's the full warning spew:
> 
> In file included from ./include/trace/define_trace.h:102,
>                  from drivers/cxl/core/trace.h:713,
>                  from drivers/cxl/core/trace.c:8:
> drivers/cxl/core/./trace.h: In function ‘trace_event_get_offsets_cxl_poison’:
> ./include/trace/stages/stage5_get_offsets.h:50:21: warning: argument 1 null where non-null expected [-Wnonnull]
>    50 |                     strlen((src) ? (const char *)(src) : "(null)") + 1)
>       |                     ^~~~~~
> ./include/trace/trace_events.h:263:9: n

The full warning didn't add any new information. The above was all I
needed. But I'm curious if you applied this patch if the warning will go
away. (Note I didn't test nor compile this).

-- Steve

diff --git a/include/trace/stages/stage5_get_offsets.h b/include/trace/stages/stage5_get_offsets.h
index e30a13be46ba..dfae18d8f4df 100644
--- a/include/trace/stages/stage5_get_offsets.h
+++ b/include/trace/stages/stage5_get_offsets.h
@@ -9,6 +9,13 @@
 #undef __entry
 #define __entry entry
 
+static inline const char *__string_src(const char *str)
+{
+	if (!str)
+		return "(null)";
+	return str;
+}
+
 /*
  * Fields should never declare an array: i.e. __field(int, arr[5])
  * If they do, it will cause issues in parsing and possibly corrupt the
@@ -47,7 +54,7 @@
 
 #undef __string
 #define __string(item, src) __dynamic_array(char, item,			\
-		    strlen((src) ? (const char *)(src) : "(null)") + 1)
+		    strlen(__string_src(src)) + 1)
 
 #undef __string_len
 #define __string_len(item, src, len) __dynamic_array(char, item, (len) + 1)