kyriazis@rpics (George Kyriazis) (05/30/89)
OK. Here is the program..
struct a {
void *pt;
} foo;
main()
{
foo.pt = (void *) &foo;
}
The compiler complains that 'pt' is not defined, on ANY system I tried
it except the SUN. What's so special about suns and/or void * ???
Am I missing something?? By void * I mean some generic kind of pointer.
George Kyriazis
kyriazis@turing.cs.rpi.edu
kyriazis@rdrc.rpi.edu
------------------------------gwyn@smoke.BRL.MIL (Doug Gwyn) (05/30/89)
In article <5197@rpi.edu> kyriazis@turing.cs.rpi.edu (George Kyriazis) writes: >Am I missing something?? By void * I mean some generic kind of pointer. What you're missing is that void* is a fairly recent innovation, and many existing UNIX C compilers don't yet support it.
ark@alice.UUCP (Andrew Koenig) (05/30/89)
In article <5197@rpi.edu>, kyriazis@rpics (George Kyriazis) writes: struct a { void *pt; } foo; main() { foo.pt = (void *) &foo; } > The compiler complains that 'pt' is not defined, on ANY system I tried > it except the SUN. What's so special about suns and/or void * ??? It works fine here. Are you sure you transcribed it correctly on those other machines? I don't see anything obviously wrong. -- --Andrew Koenig ark@europa.att.com
sandy@conexch.UUCP (Sandford Zelkovitz) (05/31/89)
In article <5197@rpi.edu>, kyriazis@rpics (George Kyriazis) writes: > > OK. Here is the program.. > struct a { > void *pt; > } foo; > main() > { > foo.pt = (void *) &foo; > } > The compiler complains that 'pt' is not defined, on ANY system I tried > it except the SUN. What's so special about suns and/or void * ??? I compiled your example under Xenix386 without any complaints from the compiler. Sanford <sandy> Zelkovitz XBBS 714-898-8634
chris@mimsy.UUCP (Chris Torek) (05/31/89)
In article <5197@rpi.edu> kyriazis@rpics (George Kyriazis) writes: > void *pt; >... The compiler complains that 'pt' is not defined, on ANY system I tried >it except the SUN. What's so special about suns and/or void * ??? The systems you tried must be using a version of PCC (`Portable C Compiler'). PCC, like many compilers for many languages, keeps track not only of declared variables but also of undeclared variables, and emits an error only on the first use: main() { i = 10; /* gets an error */ i++; /* says nothing */ j++; /* gets an error */ j = i; /* says nothing */ } Through some oversight, when `void' was added to PCC, someone used a type-code number that, combined with `pointer to', matched the special value for `undeclared variable': `void *p' enters p into the symbol table as a `complain about this undeclared variable' name.% This bug is fixed in modern PCCs, including the ones on current Berkeley tapes. ----- % This is not exactly right, but is close enough for explanatory purposes.... -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163) Domain: chris@mimsy.umd.edu Path: uunet!mimsy!chris