chris@mimsy.UUCP (04/06/87)
In article <2285@ncoast.UUCP> allbery@ncoast.UUCP (Brandon Allbery) writes: >Note that varargs is defined such that it will work even on machines such as >the Pyramid which pass arguments in registers (common on RISC machines). Or on the MIPS machines. >You MUST declare only one argument -- va_alist -- and include the type of it >as "va_dcl" without a semicolon. `va_alist' and `va_dcl' are often (always?) macros. It is conceivable that on a machine that passes the first two arguments in registers and the third through nth on the stack, these might be #define va_alist _p1, _p2, _p3 #define va_dcl int _p1, _p2, _p3; in which case va_start might be #define va_start(l) { \ struct _va_info _va; \ _va.reg = 2; _va.r[1] = _p1; _va._r[0] = _p2; \ _va.addr = &_p3; \ (l) = &_va; and va_arg then #define va_arg(l, t) \ (sizeof(t) == 8 ? \ /* size always 8 or 4 in this arch. */ (ugly code to handle double float with spanning &c) : \ (--(l)->reg >= 0 ? *(t *)&(l)->r[(l)->reg] : \ ((l)->addr++, ((t *)((l)->addr))[-1]))) (and va_end would simply be defined as `}'). This would indeed preclude usage like f(fmt, va_alist) char *fmt; va_dcl { ... The reason I mention this is that in fact, on the Pyramid, Sun, and Vax (all implementations of which I am aware), usages such as that above in fact work. I wonder, then, if this has been guaranteed anywhere. Has it? (I know, I should dig out a copy of the X3J11 draft....) >(C compilers can then recognize this directly to do any special >processing needed, as for the Pyramid.) Actually, Pyramid manages it without compiler hooks. I believe MIPS uses compiler hooks, though. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) UUCP: seismo!mimsy!chris ARPA/CSNet: chris@mimsy.umd.edu
allbery@ncoast.UUCP (04/08/87)
As quoted from <6152@mimsy.UUCP> by chris@mimsy.UUCP (Chris Torek): +--------------- | In article <2285@ncoast.UUCP> allbery@ncoast.UUCP (Brandon Allbery) writes: | >Note that varargs is defined such that it will work even on machines such as | >the Pyramid which pass arguments in registers (common on RISC machines). | | Or on the MIPS machines. +--------------- All I know about the MIPS machines is that Plexus supposedly makes one of them (Plexus calls it the P/95, I think; no idea what MIPS calls it or what archi- tecture it uses, but it's Plexus's only BSD machine. Sigh.) +--------------- | >You MUST declare only one argument -- va_alist -- and include the type of it | >as "va_dcl" without a semicolon. | | The reason I mention this is that in fact, on the Pyramid, Sun, | and Vax (all implementations of which I am aware), usages such as | that above in fact work. I wonder, then, if this has been guaranteed | anywhere. Has it? (I know, I should dig out a copy of the X3J11 | draft....) +--------------- Dunno about X3J11, POSIX, /usr/group, etc., but the System V.2 docs state that varargs must be used with va_alist as the ONLY argument. Sure, it works on stack machines where typecasting is mostly size changing or punning; but the va_alist-only stuff is the only way to be compatible with all machines. +--------------- | >(C compilers can then recognize this directly to do any special | >processing needed, as for the Pyramid.) | | Actually, Pyramid manages it without compiler hooks. I believe | MIPS uses compiler hooks, though. +--------------- I've never used a Pyramid, so I was guessing. However, it makes sense that varargs should be set up so a compiler can recognize va_alist etc. as tokens and generate the appropriate code. I would guess that some architectures might still not work; the ANSI C standard would fix this by allowing the function's varargs status to be pre-declared. (I hope; I know it was under consideration once, but varargs might not be supported in a pre-declaration in the current version of P1003.1.) ++Brando -- ____ ______________ / \ / __ __ __ \ Brandon S. Allbery | QUOTE OF THE DAY: ___ | /__> / \ / \ aXcess Company | / \ | | `--, `--, 6615 Center St. #A1-105 | ` | | \__/ \__/ \__/ Mentor, OH 44060-4101 | \____/ \______________/ +1 216 974 9210 | cbatt!cwruecmp!ncoast!allbery ncoast!allbery%case.CSNET@relay.CS.NET BALLBERY (UUCP) (CSNET/Internet) (MCIMail)
mash@mips.UUCP (04/09/87)
In article <2321@ncoast.UUCP> allbery@ncoast.UUCP (Brandon Allbery) writes: >All I know about the MIPS machines is that Plexus supposedly makes one of them >(Plexus calls it the P/95, I think; no idea what MIPS calls it or what archi- >tecture it uses, but it's Plexus's only BSD machine. Sigh.) re: facts on MIPS machines 1) There's an M/500 that's been out a while, and a recently-announced M/800 (5X 11/780 & 8X, respectively). See comp.arch, <252@winchester.mips.UUCP> 2) In classic Silicon Valley style, where you often contract out manufacturing early before you have the volume to do it inhouse, Plexus builds the physical box & peripherals to our spec; we add our CPU & memories and do the integration, test, software, etc. Plexus does NOT sell this box, and it is definitely NOT called a P/95, since it is not a Plexus system. 3) It uses a MIPS R2000 RISC CPU and R2010 FPU. 4) There are 2 UNIX ports: 1 is 4.3BSD, the other is SVR3. -- -john mashey DISCLAIMER: <generic disclaimer, I speak for me only, etc> UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!mash, DDD: 408-720-1700, x253 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
d90-pan@sm.luth.se (Per Andersson) (02/07/91)
I have a big problem using the varargs library.
What I want to do is to write a function that takes a variable number of
arguments and simply passes them on to another function like this:
a_func( va_alist )
va_dcl
{
...
b_func( va_alist );
...
};
With this definition I would be able to write something like:
a_func( "Hello world!", 42, &buf, 0 );
wich would result in b_func being called whith the same arguments.
Unfortunatley, this doesn't work to well.
The only thing I want to do is to pass ALL arguments on to b_func. It should
work like an indirect call to b_func.
Please help me!
By the way, I'm using a Sun 3-60 with SunOs V4.
| Per Andersson | c/o Boman | Voice natl. 0920 - 164 47 |
| University of Luleaa | Kungsgatan 16 | intl. +46 920 164 47 |
| SWEDEN | S-951 32 Luleaa | Internet: d90-pan@sm.luth.se |gwyn@smoke.brl.mil (Doug Gwyn) (02/08/91)
In article <1428@tau.sm.luth.se> d90-pan@sm.luth.se (Per Andersson) writes: >I have a big problem using the varargs library. True. >What I want to do is to write a function that takes a variable number of >arguments and simply passes them on to another function like this: > a_func( va_alist ) > va_dcl > { > b_func( va_alist ); > }; a_func( va_alist ) va_dcl { va_list ap; va_start( ap ); b_func( ap ); va_end( ap ); } b_func( ap ) va_list ap; { char *fmt = va_arg( ap, char * ); ... }