compiler warnings and syscall macros

compiler warnings and syscall macros

[Chris Friesen]

I'm trying to figure something out.  For ppc, in asm/unistd.h, 
__syscall_nr is defined as:


#define __syscall_nr(nr, type, name, args...)	\
	unsigned long __sc_ret, __sc_err;	\
	{					\
<snipped for brevity>
	}					\
	if (__sc_err & 0x10000000)		\
	{					\
		errno = __sc_ret;		\
		__sc_ret = -1;			\
	}					\
	return (type) __sc_ret


Whenever I use this in my code, I get compiler warnings about the 
statment "__sc_ret = -1" since it is assigning a negative value to an 
unsigned int.

Would it hurt anything if I put in an explicit cast, like this?

__sc_ret = (unsigned long) -1;

This seems to get rid of the warnings, and I can't imagine it hurting 
anything.

Am I missing something bad here?


Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com

Re: compiler warnings and syscall macros

[Tommy Reynolds]

Uttered Chris Friesen <cfriesen@nortelnetworks.com>, spoke thus:

> Would it hurt anything if I put in an explicit cast, like this?
> 
> __sc_ret = (unsigned long) -1;

Why not do the obvious:

	__sc_ret = -1UL;

and use a proper constant?

Re: compiler warnings and syscall macros

[H. Peter Anvin]

Followup to:  <3F6F6B1B.9040609@nortelnetworks.com>
By author:    Chris Friesen <cfriesen@nortelnetworks.com>
In newsgroup: linux.dev.kernel
>
> 
> I'm trying to figure something out.  For ppc, in asm/unistd.h, 
> __syscall_nr is defined as:
> 
> 
> #define __syscall_nr(nr, type, name, args...)	\
> 	unsigned long __sc_ret, __sc_err;	\
> 	{					\
> <snipped for brevity>
> 	}					\
> 	if (__sc_err & 0x10000000)		\
> 	{					\
> 		errno = __sc_ret;		\
> 		__sc_ret = -1;			\
> 	}					\
> 	return (type) __sc_ret
> 
> 
> Whenever I use this in my code, I get compiler warnings about the 
> statment "__sc_ret = -1" since it is assigning a negative value to an 
> unsigned int.

Just do:

__sc_ret = -1UL;

	-hpa

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
If you send me mail in HTML format I will assume it's spam.
"Unix gives you enough rope to shoot yourself in the foot."
Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64

Re: compiler warnings and syscall macros

[H. Peter Anvin]

Followup to:  <3F6F6B1B.9040609@nortelnetworks.com>
By author:    Chris Friesen <cfriesen@nortelnetworks.com>
In newsgroup: linux.dev.kernel
>
> 
> I'm trying to figure something out.  For ppc, in asm/unistd.h, 
> __syscall_nr is defined as:
> 
> 
> #define __syscall_nr(nr, type, name, args...)	\
> 	unsigned long __sc_ret, __sc_err;	\
> 	{					\
> <snipped for brevity>
> 	}					\
> 	if (__sc_err & 0x10000000)		\
> 	{					\
> 		errno = __sc_ret;		\
> 		__sc_ret = -1;			\
> 	}					\
> 	return (type) __sc_ret
> 
> 
> Whenever I use this in my code, I get compiler warnings about the 
> statment "__sc_ret = -1" since it is assigning a negative value to an 
> unsigned int.

Just do:

__sc_ret = -1UL;

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
If you send me mail in HTML format I will assume it's spam.
"Unix gives you enough rope to shoot yourself in the foot."
Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64

Re: compiler warnings and syscall macros

[H. Peter Anvin]

Followup to:  <200309222253.PAA21087@cesium.transmeta.com>
By author:    "H. Peter Anvin" <hpa@zytor.com>
In newsgroup: linux.dev.kernel
> 
> Just do:
> 
> __sc_ret = -1UL;
> 
> 	-hpa

... sorry for the dupes; client said post hadn't happened when in fact
it had.

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
If you send me mail in HTML format I will assume it's spam.
"Unix gives you enough rope to shoot yourself in the foot."
Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64

Re: compiler warnings and syscall macros

[Chris Friesen]

Tommy Reynolds wrote:

> Why not do the obvious:
> 
> 	__sc_ret = -1UL;
> 
> and use a proper constant?


Cause I'm not thinking straight?

Chris


-- 
Chris Friesen                    | MailStop: 043/33/F10
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com