* [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
@ 2019-09-25 17:29 Nathan Chancellor
2019-09-25 17:41 ` Nick Desaulniers
2019-09-26 16:22 ` [PATCH v2] " Nathan Chancellor
0 siblings, 2 replies; 5+ messages in thread
From: Nathan Chancellor @ 2019-09-25 17:29 UTC (permalink / raw)
To: Steven Rostedt, Ingo Molnar
Cc: linux-kernel, clang-built-linux, Nick Desaulniers,
David Bolvansky, Nathan Chancellor
After r372664 in clang, the IF_ASSIGN macro causes a couple hundred
warnings along the lines of:
kernel/trace/trace_output.c:1331:2: warning: converting the enum
constant to a boolean [-Wint-in-bool-context]
kernel/trace/trace.h:409:3: note: expanded from macro
'trace_assign_type'
IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,
^
kernel/trace/trace.h:371:14: note: expanded from macro 'IF_ASSIGN'
WARN_ON(id && (entry)->type != id); \
^
264 warnings generated.
Add the implicit '!= 0' to the WARN_ON statement to fix the warnings.
Link: https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b
Link: https://github.com/ClangBuiltLinux/linux/issues/686
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
kernel/trace/trace.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 26b0a08f3c7d..f801d154ff6a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -365,11 +365,11 @@ static inline struct trace_array *top_trace_array(void)
__builtin_types_compatible_p(typeof(var), type *)
#undef IF_ASSIGN
-#define IF_ASSIGN(var, entry, etype, id) \
- if (FTRACE_CMP_TYPE(var, etype)) { \
- var = (typeof(var))(entry); \
- WARN_ON(id && (entry)->type != id); \
- break; \
+#define IF_ASSIGN(var, entry, etype, id) \
+ if (FTRACE_CMP_TYPE(var, etype)) { \
+ var = (typeof(var))(entry); \
+ WARN_ON(id != 0 && (entry)->type != id); \
+ break; \
}
/* Will cause compile errors if type is not found. */
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
2019-09-25 17:29 [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro Nathan Chancellor
@ 2019-09-25 17:41 ` Nick Desaulniers
2019-09-25 23:41 ` Dávid Bolvanský
[not found] ` <CAOrgDVMqOqKtY-9FNV5iHWmz6GFqsH=ugwYp77Zwfr3Niw0ebg@mail.gmail.com>
2019-09-26 16:22 ` [PATCH v2] " Nathan Chancellor
1 sibling, 2 replies; 5+ messages in thread
From: Nick Desaulniers @ 2019-09-25 17:41 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Steven Rostedt, Ingo Molnar, LKML, clang-built-linux, David Bolvansky
On Wed, Sep 25, 2019 at 10:29 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> After r372664 in clang, the IF_ASSIGN macro causes a couple hundred
> warnings along the lines of:
>
> kernel/trace/trace_output.c:1331:2: warning: converting the enum
> constant to a boolean [-Wint-in-bool-context]
> kernel/trace/trace.h:409:3: note: expanded from macro
> 'trace_assign_type'
> IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,
> ^
> kernel/trace/trace.h:371:14: note: expanded from macro 'IF_ASSIGN'
> WARN_ON(id && (entry)->type != id); \
> ^
> 264 warnings generated.
>
> Add the implicit '!= 0' to the WARN_ON statement to fix the warnings.
>
> Link: https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b
> Link: https://github.com/ClangBuiltLinux/linux/issues/686
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
I can't think of a case that this warning is a bug (maybe David can
explain more), but seems like a small fix that can stop a big spew of
warnings, and IIUC this is the lone instance we see in the kernel. In
that case, I prefer a tiny change to outright disabling the warning in
case it does find interesting cases later.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> kernel/trace/trace.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 26b0a08f3c7d..f801d154ff6a 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -365,11 +365,11 @@ static inline struct trace_array *top_trace_array(void)
> __builtin_types_compatible_p(typeof(var), type *)
>
> #undef IF_ASSIGN
> -#define IF_ASSIGN(var, entry, etype, id) \
> - if (FTRACE_CMP_TYPE(var, etype)) { \
> - var = (typeof(var))(entry); \
> - WARN_ON(id && (entry)->type != id); \
> - break; \
> +#define IF_ASSIGN(var, entry, etype, id) \
> + if (FTRACE_CMP_TYPE(var, etype)) { \
> + var = (typeof(var))(entry); \
> + WARN_ON(id != 0 && (entry)->type != id); \
> + break; \
> }
>
> /* Will cause compile errors if type is not found. */
> --
> 2.23.0
>
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
2019-09-25 17:41 ` Nick Desaulniers
@ 2019-09-25 23:41 ` Dávid Bolvanský
[not found] ` <CAOrgDVMqOqKtY-9FNV5iHWmz6GFqsH=ugwYp77Zwfr3Niw0ebg@mail.gmail.com>
1 sibling, 0 replies; 5+ messages in thread
From: Dávid Bolvanský @ 2019-09-25 23:41 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Nathan Chancellor, Steven Rostedt, Ingo Molnar, LKML, clang-built-linux
GCC C frontend does not warn, GCC C++ FE does. https://godbolt.org/z/_sczyM
So I (we?) think there is something weird in gcc frontends.
>> I can't think of a case that this warning is a bug (maybe David can
explain more),
In this case or generally? General bug example:
if (state == A || B)
(should be if (state == A || state == B))
Since this is just one occurrence and I recommend to just land this small fix.
st 25. 9. 2019 o 19:41 Nick Desaulniers <ndesaulniers@google.com> napísal(a):
>
> On Wed, Sep 25, 2019 at 10:29 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > After r372664 in clang, the IF_ASSIGN macro causes a couple hundred
> > warnings along the lines of:
> >
> > kernel/trace/trace_output.c:1331:2: warning: converting the enum
> > constant to a boolean [-Wint-in-bool-context]
> > kernel/trace/trace.h:409:3: note: expanded from macro
> > 'trace_assign_type'
> > IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,
> > ^
> > kernel/trace/trace.h:371:14: note: expanded from macro 'IF_ASSIGN'
> > WARN_ON(id && (entry)->type != id); \
> > ^
> > 264 warnings generated.
> >
> > Add the implicit '!= 0' to the WARN_ON statement to fix the warnings.
> >
> > Link: https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b
> > Link: https://github.com/ClangBuiltLinux/linux/issues/686
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
>
> I can't think of a case that this warning is a bug (maybe David can
> explain more), but seems like a small fix that can stop a big spew of
> warnings, and IIUC this is the lone instance we see in the kernel. In
> that case, I prefer a tiny change to outright disabling the warning in
> case it does find interesting cases later.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
> > ---
> > kernel/trace/trace.h | 10 +++++-----
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > index 26b0a08f3c7d..f801d154ff6a 100644
> > --- a/kernel/trace/trace.h
> > +++ b/kernel/trace/trace.h
> > @@ -365,11 +365,11 @@ static inline struct trace_array *top_trace_array(void)
> > __builtin_types_compatible_p(typeof(var), type *)
> >
> > #undef IF_ASSIGN
> > -#define IF_ASSIGN(var, entry, etype, id) \
> > - if (FTRACE_CMP_TYPE(var, etype)) { \
> > - var = (typeof(var))(entry); \
> > - WARN_ON(id && (entry)->type != id); \
> > - break; \
> > +#define IF_ASSIGN(var, entry, etype, id) \
> > + if (FTRACE_CMP_TYPE(var, etype)) { \
> > + var = (typeof(var))(entry); \
> > + WARN_ON(id != 0 && (entry)->type != id); \
> > + break; \
> > }
> >
> > /* Will cause compile errors if type is not found. */
> > --
> > 2.23.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
[not found] ` <CAOrgDVMqOqKtY-9FNV5iHWmz6GFqsH=ugwYp77Zwfr3Niw0ebg@mail.gmail.com>
@ 2019-09-26 12:15 ` Steven Rostedt
0 siblings, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2019-09-26 12:15 UTC (permalink / raw)
To: Dávid Bolvanský
Cc: Nick Desaulniers, Nathan Chancellor, Ingo Molnar, LKML,
clang-built-linux
On Thu, 26 Sep 2019 01:37:29 +0200
Dávid Bolvanský <david.bolvansky@gmail.com> wrote:
> GCC C frontend does not warn, GCC C++ FE does. https://godbolt.org/z/_sczyM
>
> So I (we?) think there is something weird in gcc frontends.
>
> >> I can't think of a case that this warning is a bug (maybe David can
> explain more),
>
> In this case or generally? General bug example:
>
> if (state == A || B)
>
> (should be if (state == A || state == B))
>
> Since this is just one occurrence and I recommend to just land this small
> fix.
>
Can we add the above comment to the commit log. I was stuck on
wondering what was wrong with the original code, and was ignoring the
patch because I couldn't see what was wrong.
-- Steve
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
2019-09-25 17:29 [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro Nathan Chancellor
2019-09-25 17:41 ` Nick Desaulniers
@ 2019-09-26 16:22 ` Nathan Chancellor
1 sibling, 0 replies; 5+ messages in thread
From: Nathan Chancellor @ 2019-09-26 16:22 UTC (permalink / raw)
To: Steven Rostedt, Ingo Molnar
Cc: linux-kernel, clang-built-linux, David Bolvansky,
Nathan Chancellor, Nick Desaulniers
After r372664 in clang, the IF_ASSIGN macro causes a couple hundred
warnings along the lines of:
kernel/trace/trace_output.c:1331:2: warning: converting the enum
constant to a boolean [-Wint-in-bool-context]
kernel/trace/trace.h:409:3: note: expanded from macro
'trace_assign_type'
IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,
^
kernel/trace/trace.h:371:14: note: expanded from macro 'IF_ASSIGN'
WARN_ON(id && (entry)->type != id); \
^
264 warnings generated.
This warning can catch issues with constructs like:
if (state == A || B)
where the developer really meant:
if (state == A || state == B)
This is currently the only occurrence of the warning in the kernel
tree across defconfig, allyesconfig, allmodconfig for arm32, arm64,
and x86_64. Add the implicit '!= 0' to the WARN_ON statement to fix
the warnings and find potential issues in the future.
Link: https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b
Link: https://github.com/ClangBuiltLinux/linux/issues/686
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
v1 -> v2:
* Update commit message to give context behind the warning and explain
this is currently the only occurrence of this warning in the tree.
* Add Nick's Reviewed-by tag.
kernel/trace/trace.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 26b0a08f3c7d..f801d154ff6a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -365,11 +365,11 @@ static inline struct trace_array *top_trace_array(void)
__builtin_types_compatible_p(typeof(var), type *)
#undef IF_ASSIGN
-#define IF_ASSIGN(var, entry, etype, id) \
- if (FTRACE_CMP_TYPE(var, etype)) { \
- var = (typeof(var))(entry); \
- WARN_ON(id && (entry)->type != id); \
- break; \
+#define IF_ASSIGN(var, entry, etype, id) \
+ if (FTRACE_CMP_TYPE(var, etype)) { \
+ var = (typeof(var))(entry); \
+ WARN_ON(id != 0 && (entry)->type != id); \
+ break; \
}
/* Will cause compile errors if type is not found. */
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2019-09-25 17:29 [PATCH] tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro Nathan Chancellor
2019-09-25 17:41 ` Nick Desaulniers
2019-09-25 23:41 ` Dávid Bolvanský
[not found] ` <CAOrgDVMqOqKtY-9FNV5iHWmz6GFqsH=ugwYp77Zwfr3Niw0ebg@mail.gmail.com>
2019-09-26 12:15 ` Steven Rostedt
2019-09-26 16:22 ` [PATCH v2] " Nathan Chancellor
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