Re: [PATCH v1 02/48] tools headers: Silence -Wshorten-64-to-32 warnings

[Yury Norov <yury.norov@gmail.com>]

On Tue, Apr 01, 2025 at 11:23:00AM -0700, Ian Rogers wrote:
> The clang warning -Wshorten-64-to-32 can be useful to catch
> inadvertent truncation. In some instances this truncation can lead to
> changing the sign of a result, for example, truncation to return an
> int to fit a sort routine. Silence the warning by making the implicit
> truncation explicit.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/include/asm-generic/bitops/fls64.h | 2 +-
>  tools/include/linux/bitfield.h           | 2 +-
>  tools/include/linux/bitmap.h             | 2 +-
>  tools/include/linux/err.h                | 2 +-
>  tools/include/linux/hash.h               | 2 +-
>  tools/include/linux/math64.h             | 2 +-
>  6 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/include/asm-generic/bitops/fls64.h b/tools/include/asm-generic/bitops/fls64.h
> index 866f2b2304ff..9ad3ff12f454 100644
> --- a/tools/include/asm-generic/bitops/fls64.h
> +++ b/tools/include/asm-generic/bitops/fls64.h
> @@ -21,7 +21,7 @@ static __always_inline int fls64(__u64 x)
>  	__u32 h = x >> 32;
>  	if (h)
>  		return fls(h) + 32;
> -	return fls(x);
> +	return fls((__u32)x);

Can you keep kernel and tools sources synchronized?

>  }
>  #elif BITS_PER_LONG == 64
>  static __always_inline int fls64(__u64 x)
> diff --git a/tools/include/linux/bitfield.h b/tools/include/linux/bitfield.h
> index 6093fa6db260..aa0b8e52214f 100644
> --- a/tools/include/linux/bitfield.h
> +++ b/tools/include/linux/bitfield.h
> @@ -146,7 +146,7 @@ static __always_inline __##type type##_encode_bits(base v, base field)	\
>  {									\
>  	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
>  		__field_overflow();					\
> -	return to((v & field_mask(field)) * field_multiplier(field));	\
> +	return to((__##type)((v & field_mask(field)) * field_multiplier(field))); \
>  }									\
>  static __always_inline __##type type##_replace_bits(__##type old,	\
>  					base val, base field)		\
> diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
> index 2a7f260ef9dc..b7a7c752e4f2 100644
> --- a/tools/include/linux/bitmap.h
> +++ b/tools/include/linux/bitmap.h
> @@ -63,7 +63,7 @@ static inline bool bitmap_full(const unsigned long *src, unsigned int nbits)
>  	return find_first_zero_bit(src, nbits) == nbits;
>  }
>  
> -static inline unsigned int bitmap_weight(const unsigned long *src, unsigned int nbits)
> +static inline unsigned long bitmap_weight(const unsigned long *src, unsigned int nbits)
>  {
>  	if (small_const_nbits(nbits))
>  		return hweight_long(*src & BITMAP_LAST_WORD_MASK(nbits));

Oh no... bitmap_weight() is used in printk(), and you'll get tons of
warnings because, say %x should be replaced with %lx. 

> diff --git a/tools/include/linux/err.h b/tools/include/linux/err.h
> index 332b983ead1e..9c1746e3696d 100644
> --- a/tools/include/linux/err.h
> +++ b/tools/include/linux/err.h

I don't maintain the this and the following subsystems. Can you make
it a separate patch?

> @@ -55,7 +55,7 @@ static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
>  static inline int __must_check PTR_ERR_OR_ZERO(__force const void *ptr)
>  {
>  	if (IS_ERR(ptr))
> -		return PTR_ERR(ptr);
> +		return (int)PTR_ERR(ptr);
>  	else
>  		return 0;
>  }
> diff --git a/tools/include/linux/hash.h b/tools/include/linux/hash.h
> index 38edaa08f862..ecc8296cb397 100644
> --- a/tools/include/linux/hash.h
> +++ b/tools/include/linux/hash.h
> @@ -75,7 +75,7 @@ static __always_inline u32 hash_64_generic(u64 val, unsigned int bits)
>  {
>  #if BITS_PER_LONG == 64
>  	/* 64x64-bit multiply is efficient on all 64-bit processors */
> -	return val * GOLDEN_RATIO_64 >> (64 - bits);
> +	return (u32)(val * GOLDEN_RATIO_64 >> (64 - bits));
>  #else
>  	/* Hash 64 bits using only 32x32-bit multiply. */
>  	return hash_32((u32)val ^ __hash_32(val >> 32), bits);
> diff --git a/tools/include/linux/math64.h b/tools/include/linux/math64.h
> index 4ad45d5943dc..03d6c5220957 100644
> --- a/tools/include/linux/math64.h
> +++ b/tools/include/linux/math64.h
> @@ -48,7 +48,7 @@ static inline u64 mul_u64_u32_shr(u64 a, u32 b, unsigned int shift)
>  	u32 ah, al;
>  	u64 ret;
>  
> -	al = a;
> +	al = (u32)a;
>  	ah = a >> 32;
>  
>  	ret = mul_u32_u32(al, b) >> shift;
> -- 
> 2.49.0.504.g3bcea36a83-goog