C Compiler bugs (was Re: Speaking of ksh)

[Mat Waites]

In article <532 at wrs.UUCP> owen at wrs.UUCP (Owen DeLong) writes:
]In article <4421 at haddock.ISC.COM> karl at haddock.ima.isc.com (Karl Heuer) writes:
]>In article <15085 at tut.cis.ohio-state.edu> lvc at tut.cis.ohio-state.edu (Lawrence V. Cipriani) writes:
]>>Following up from comp.unix.wizards are amusing C Compiler bugs:
]>>Then there was the bug where if you had a structure declaration right before
]>>main and forget to end it with a ; the program would core dump on exit:
]>>	struct blob { int a, b, c; } /* missing ; */
]>>	main(argc, argv) ...
]>
]>Why should it be considered a "compiler bug" when a syntactically correct
]>program containing a user bug dumps core?  It seems to me that the appropriate
]>"fix" is to make sure that lint complains about the mismatched declaration.
]>
]>Karl W. Z. Heuer (ima!haddock!karl or karl at haddock.isc.com), The Walking Lint
]>Followups to comp.lang.c.
]
]Tell me, Karl, where do you see the bug causing the program to dump core?
]
]I get the impression that the bug is in the compiler, and the compiler which
]doesn't need a ; (noted as missing) dumped core upon trying to return from
]function main. 

[ I see a clue here! ]

]I see this as definitely being a compiler bug, particularly
]if you consider the code to be correct.  It is conceivable to call the code
]incorrect (syntax error due to missing semicolon), but I would say that the
]compiler should actually accept the closing brace on a compound statement as
]an implied ; afterwards.  If I'm wrong, flame me...I'll learn that way.  If
]I'm not, we've all learned something.  I would like to see the rest of the
]program which you must have seen to say it was a user bug.
]
]Owen


The program is syntactically correct. It declares a function named main
which returns a struct blob. Unfortunately the run-time system is not familiar
with blobs and will probably end up trashing the stack on exit.

If you'd written:

struct blob { int a, b, c; } /* missing ; */
bozo;

you'd have a struct blob called bozo. Why shouldn't main act the same way.
"main" is not a reserved word in general, although some compilers treat
it differently than other function names.

I think "the walking lint" is probably right about lint recognizing 
main's appropriate return value type (although is seems to be
somewhat implementation dependant)


Mat

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