[PATCH] system: Add WARN_UNUSED_RESULT

[PATCH] system: Add WARN_UNUSED_RESULT

[Marek Polacek]

I'd like to have the option of marking functions with
__attribute__ ((__warn_unused_result__)), so this patch adds a macro.
And use it for maybe_wrap_with_location, it's always a bug if the
return value is not used, which happened to me and got me confused.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

gcc/ChangeLog:

	* system.h (WARN_UNUSED_RESULT): Define for GCC >= 3.4.
	* tree.h (maybe_wrap_with_location): Add WARN_UNUSED_RESULT.
---
 gcc/system.h | 6 ++++++
 gcc/tree.h   | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/system.h b/gcc/system.h
index b0f3f1dd019..6f6ab616a61 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -789,6 +789,12 @@ extern void fancy_abort (const char *, int, const char *)
 #define ALWAYS_INLINE inline
 #endif
 
+#if GCC_VERSION >= 3004
+#define WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
+#else
+#define WARN_UNUSED_RESULT
+#endif
+
 /* Use gcc_unreachable() to mark unreachable locations (like an
    unreachable default case of a switch.  Do not use gcc_assert(0).  */
 #if (GCC_VERSION >= 4005) && !ENABLE_ASSERT_CHECKING
diff --git a/gcc/tree.h b/gcc/tree.h
index 684be10b440..9a713cdb0c7 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1214,7 +1214,7 @@ get_expr_source_range (tree expr)
 extern void protected_set_expr_location (tree, location_t);
 extern void protected_set_expr_location_if_unset (tree, location_t);
 
-extern tree maybe_wrap_with_location (tree, location_t);
+WARN_UNUSED_RESULT extern tree maybe_wrap_with_location (tree, location_t);
 
 extern int suppress_location_wrappers;
 

base-commit: 0f5f9ed5e5a041b636cc002451b1e8b2295f8e4f
-- 
2.28.0

Re: [PATCH] system: Add WARN_UNUSED_RESULT

[Jason Merrill]

On 11/11/20 10:03 PM, Marek Polacek wrote:
> I'd like to have the option of marking functions with
> __attribute__ ((__warn_unused_result__)), so this patch adds a macro.
> And use it for maybe_wrap_with_location, it's always a bug if the
> return value is not used, which happened to me and got me confused.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> gcc/ChangeLog:
> 
> 	* system.h (WARN_UNUSED_RESULT): Define for GCC >= 3.4.
> 	* tree.h (maybe_wrap_with_location): Add WARN_UNUSED_RESULT.
> ---
>   gcc/system.h | 6 ++++++
>   gcc/tree.h   | 2 +-
>   2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/system.h b/gcc/system.h
> index b0f3f1dd019..6f6ab616a61 100644
> --- a/gcc/system.h
> +++ b/gcc/system.h
> @@ -789,6 +789,12 @@ extern void fancy_abort (const char *, int, const char *)
>   #define ALWAYS_INLINE inline
>   #endif
>   
> +#if GCC_VERSION >= 3004
> +#define WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
> +#else
> +#define WARN_UNUSED_RESULT
> +#endif
> +
>   /* Use gcc_unreachable() to mark unreachable locations (like an
>      unreachable default case of a switch.  Do not use gcc_assert(0).  */
>   #if (GCC_VERSION >= 4005) && !ENABLE_ASSERT_CHECKING
> diff --git a/gcc/tree.h b/gcc/tree.h
> index 684be10b440..9a713cdb0c7 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -1214,7 +1214,7 @@ get_expr_source_range (tree expr)
>   extern void protected_set_expr_location (tree, location_t);
>   extern void protected_set_expr_location_if_unset (tree, location_t);
>   
> -extern tree maybe_wrap_with_location (tree, location_t);
> +WARN_UNUSED_RESULT extern tree maybe_wrap_with_location (tree, location_t);
>   
>   extern int suppress_location_wrappers;
>   
> 
> base-commit: 0f5f9ed5e5a041b636cc002451b1e8b2295f8e4f
>