Date: Sun, 17 May 2015 22:42:24 +1000 From: andrew clarke <mail@ozzmosis.com> To: Ian Smith <smithi@nimnet.asn.au> Cc: freebsd-questions@freebsd.org, Trev Roydhouse <trev@sentry.org> Subject: Re: Strange return codes from old but good C program Message-ID: <20150517124223.GA82704@ozzmosis.com> In-Reply-To: <20150517204503.V69409@sola.nimnet.asn.au> References: <20150517204503.V69409@sola.nimnet.asn.au>
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On Sun 2015-05-17 22:16:14 UTC+1000, Ian Smith (smithi@nimnet.asn.au) wrote: > Hi, > > I'm hoping someone can help me figure out the behaviour of a C program > executed repeatedly from a shell invoked by my freepascal program. > > If anyone might care to download <http://www.moshier.net/de118i-2.zip>; > (258071 bytes), unzip it and run 'make', the supplied makefile - a copy > of unixl.mak - should provide ssystem compiled for long double precision > maths, just as I wanted, with the following output from gcc from FreeBSD > 4.5 to 9.3-RELEASE. (If clang has trouble on 10.X, please let me know) That makefile defaults to gcc but allows you to build it with clang (which spits out a bunch of warnings similar to gcc) using: make -f unixl.mak CC=clang > smithi@x200:~/de118i-2 % make > gcc -O2 -c ssystem.c > ssystem.c: In function 'resstate': > ssystem.c:150: warning: incompatible implicit declaration of built-in > function 'exit' > ssystem.c: In function 'main': > ssystem.c:180: warning: incompatible implicit declaration of built-in > function 'malloc' stdlib.h provides prototypes for exit() and malloc(). #include <stdlib.h> > ssystem runs as well as ever, these warnings indicate no functional > issues, but they do highlight the author's poor (but unsurprising in > 1993, last updated 2004) choice of return codes both for real errors > (malloc, file I/O, and maths div by zero, bad args for trig functions > and such) which mostly exit(1) but some return 0 (!) - but when ending > successfully it returns _usually_ 22, but sometimes 11, or 10, both seen > so far, consistently when run with the same (different) parameters. The code looks like ancient K&R C, which was a lot more relaxed with syntax than modern ISO C compilers. Even by 1993, most C developers had moved on from K&R. > What's worse is I can't figure out where in ssystem.c any return code > might be set on completion of main(), which is just declared as: > > main() > { This is fine in K&R, but the ISO C prototype for main() without arguments is: int main(void); > and ends with the last of its results and (accuracy) errors printf()s: > > ii += 6; > } > #if FPESHOW # floating point debug, here set to 0 > fperem(); > #endif > } /* end of main program */ > > No variables called rc or anysuch .. so what sets these odd retcodes? Normally you'd use a return statement, eg. #include <stdio.h> /* prototype for printf() */ int main(void) { printf("Hello world.\n"); /* say hi */ return 0; /* return zero to the OS */ } I haven't checked the standard but it's plausible that the ISO C spec allows a random return code if none is given, especially if no prototype for main() is provided. There may be tools around to convert K&R C code to ANSI/ISO C syntax, rather than trying to do it by hand. The code may still need some tweaking, though, eg. return 0 from main(). > I'd be grateful for any clue. So far I assume any return code > 1 is > success, so far so good - but it doesn't feel deterministic enough :) > > cheers, Ian (please cc me, I'm subscribed to the digest) Pretty sure I know you from FidoNet, years ago. Also Trev Roydhouse. AUST_C_HERE, or another echo, maybe? Regards Andrew
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