[PATCH] bpf: define INT8_TYPE as signed char

[PATCH] bpf: define INT8_TYPE as signed char

[David Faust]

Change the BPF backend to define INT8_TYPE with an explicit sign, rather
than a plain char.  This is in line with other targets and removes the
risk of int8_t being affected by the signedness of the plain char type
of the host system.

Tested on x86_64-linux-gnu host for bpf-unknown-none.
Sanity checked compiling Linux kernel BPF selftests.

gcc/

	* config/bpf/bpf.h (INT8_TYPE): Change to signed char.
---
 gcc/config/bpf/bpf.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
index f107a5a4c34..3cc5daa1b58 100644
--- a/gcc/config/bpf/bpf.h
+++ b/gcc/config/bpf/bpf.h
@@ -99,7 +99,7 @@
 
 #define SIG_ATOMIC_TYPE "char"
 
-#define INT8_TYPE "char"
+#define INT8_TYPE "signed char"
 #define INT16_TYPE "short int"
 #define INT32_TYPE "int"
 #define INT64_TYPE "long int"
-- 
2.43.0

Re: [PATCH] bpf: define INT8_TYPE as signed char

[Jose E. Marchesi]

Hi David.

> Change the BPF backend to define INT8_TYPE with an explicit sign, rather
> than a plain char.  This is in line with other targets and removes the
> risk of int8_t being affected by the signedness of the plain char type
> of the host system.

OK.

I would add to the commit message that the motivation for this change is
that even if `char' is defined to be signed in BPF targets, some BPF
programs use the (mal)practice of including internal libc headers
indirectly via kernel headers and that may trigger compilation errors
regarding redefinitions of types.

Thanks for the patch!

>
> Tested on x86_64-linux-gnu host for bpf-unknown-none.
> Sanity checked compiling Linux kernel BPF selftests.
>
> gcc/
>
> 	* config/bpf/bpf.h (INT8_TYPE): Change to signed char.
> ---
>  gcc/config/bpf/bpf.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
> index f107a5a4c34..3cc5daa1b58 100644
> --- a/gcc/config/bpf/bpf.h
> +++ b/gcc/config/bpf/bpf.h
> @@ -99,7 +99,7 @@
>  
>  #define SIG_ATOMIC_TYPE "char"
>  
> -#define INT8_TYPE "char"
> +#define INT8_TYPE "signed char"
>  #define INT16_TYPE "short int"
>  #define INT32_TYPE "int"
>  #define INT64_TYPE "long int"

Re: [PATCH] bpf: define INT8_TYPE as signed char

[David Faust]

On 3/14/24 10:16, Jose E. Marchesi wrote:
> 
> Hi David.
> 
>> Change the BPF backend to define INT8_TYPE with an explicit sign, rather
>> than a plain char.  This is in line with other targets and removes the
>> risk of int8_t being affected by the signedness of the plain char type
>> of the host system.
> 
> OK.
> 
> I would add to the commit message that the motivation for this change is
> that even if `char' is defined to be signed in BPF targets, some BPF
> programs use the (mal)practice of including internal libc headers
> indirectly via kernel headers and that may trigger compilation errors
> regarding redefinitions of types.

Thanks, added this to the commit message and pushed.

> 
> Thanks for the patch!
> 
>>
>> Tested on x86_64-linux-gnu host for bpf-unknown-none.
>> Sanity checked compiling Linux kernel BPF selftests.
>>
>> gcc/
>>
>> 	* config/bpf/bpf.h (INT8_TYPE): Change to signed char.
>> ---
>>  gcc/config/bpf/bpf.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
>> index f107a5a4c34..3cc5daa1b58 100644
>> --- a/gcc/config/bpf/bpf.h
>> +++ b/gcc/config/bpf/bpf.h
>> @@ -99,7 +99,7 @@
>>  
>>  #define SIG_ATOMIC_TYPE "char"
>>  
>> -#define INT8_TYPE "char"
>> +#define INT8_TYPE "signed char"
>>  #define INT16_TYPE "short int"
>>  #define INT32_TYPE "int"
>>  #define INT64_TYPE "long int"