Date: Thu, 29 Oct 1998 05:53:44 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: hackers@FreeBSD.ORG Subject: compiler prototype question... Message-ID: <199810290453.FAA07168@labinfo.iet.unipi.it>
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Hi,
can someone tell me why in the following C program:
int c1 (int c);
int c1 (char c) { return 1 ; }
Hi,
can someone tell me why in the following C program:
int c1 (int c);
int c1 (char c) { return 1 ; }
int c2 (int c);
int c2 (c) char c; { return 1 ; }
int c3 (char c);
int c3 (c) int c; { return 1 ;}
int c4 (char c);
int c4 (int c) { return 1 ;}
compiled on 2.2.6 produces this output:
prova# cc -c -Wall proto.c
proto.c:8: conflicting types for `c1'
proto.c:7: previous declaration of `c1'
proto.c: In function `c3':
proto.c:14: argument `c' doesn't match prototype
proto.c:13: prototype declaration
proto.c: At top level:
proto.c:17: conflicting types for `c4'
proto.c:16: previous declaration of `c4'
To me, c2() seems as bad as the others, and i don't understand why
the compiler does not complain. It seems that when the prototype
declares an "int" argument, then any signed/unsigned type is accepted
for that argument in the non-ansi function body. As you can imagine
this defeats the usefulness of prototypes and obfuscates code.
Furthermore, with multiple arguments, i could even be suspicious of
how the compiler behaves (e.g. does it push a wordsize argument
and then tries to read it as multiple 1 or 2 byte items ?).
and the reason i am asking on hackers...
there is such code in the kernel, e.g. sys/i386/isa/if_ed.c
function ed_get_packet() has this problem and i don't know if it
a bug or what.
cheers
luigi
-----------------------------+--------------------------------------
Luigi Rizzo | Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it | Universita' di Pisa
tel: +39-50-568533 | via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 | http://www.iet.unipi.it/~luigi/
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