How comes the compiler doesn't complain about conflicting variables for the following piece of code..
Chad
#include <stdio.h>
enum values {
I = 1,
V = 5,
X = 10,
L = 50,
C = 100,
D = 500,
M = 1000
};
int main(void)
{
int D = 44;
enum values romandigits = D;
printf("The value is: %d\n", romandigits);
return 0;
}
I get....
[cdalten@localhost oakland]$ gcc -g -Wall -Wextra roman.c -o roman
[cdalten@localhost oakland]$ ./roman
The value is: 44
[cdalten@localhost oakland]$
How come the compiler doesn't complain about 'D' being both an int and
an enum?
Chad
Eric Sosman
The inner declaration in the contained scope "shadows" or
"hides" the outer declaration in the containing scope.
int x = 42;
// `x' refers to the file-scope int
void f(void) {
// `x' still refers to the file-scope int
double x = 42.0;
// `x' now refers to a local double
int i;
for (i = 0; i < 10; ++i) {
// `x' still refers to the local double
char x[100];
// `x' now refers to a local array of char
...
}
// `x' refers to the local double again
...
}
// `x' refers to the file-scope int again
--
Eric Sosman
eso...@ieee-dot-org.invalid
Alexander Bartolich
> [...] How come the compiler doesn't complain about 'D' being both
> an int and an enum?
Because the declarations are in different scopes.
You do get an error if they are in the same scope.
And no, it's a feature.
--
bartc
"Chad" <cda...@gmail.com> wrote in message
news:f12bba4f-44b7-4b54...@z11g2000yqz.googlegroups.com...
int D is in a local scope, it hides the outer D.
Try moving enum values{} inside main().
--
Bartc
christian.bau
> How come the compiler doesn't complain about 'D' being both an int and
> an enum?
Both D's are in different scopes. The int D is enclosed in { } and
therefore D will always mean the "int D" within those braces. You
could even write
int main (void)
{
int D = 44;
{
int D = 113;
printf ("%d\n", D); // prints 113
}
printf ("%d\n", D); // prints 44
}
Ben Bacarisse
<snip>
> enum values {
<snip>
> D = 500,
> M = 1000
> };
>
> int main(void)
> {
> int D = 44;
> enum values romandigits = D;
> printf("The value is: %d\n", romandigits);
> return 0;
> }
>
> I get....
> [cdalten@localhost oakland]$ gcc -g -Wall -Wextra roman.c -o roman
> [cdalten@localhost oakland]$ ./roman
> The value is: 44
>
> an enum?
You might choose to add -Wshaddow to your set of useful gcc options.
--
Ben.
Dann Corbit
<0.e4c2cbedea2b6a7e77f1.2010...@bsb.me.uk>,
ben.u...@bsb.me.uk says...
Lint is also handy:
C:\tmp>"C:\Lint\Lint-nt" +v -i"C:\Lint" std.lnt -os(_LINT.TMP) l.c
PC-lint for C/C++ (NT) Vers. 8.00u, Copyright Gimpel Software 1985-2006
--- Module: l.c (C)
C:\tmp>type _LINT.TMP | more
--- Module: l.c (C)
_
int D = 44;
l.c(15) : Warning 578: Declaration of symbol 'D' hides symbol
'values::D' (line
9)
l.c(9) : Info 830: Location cited in prior message
_
enum values romandigits = D;
l.c(16) : Error 64: Type mismatch (initialization) (int/enum)
_
}
l.c(19) : Note 953: Variable 'D' (line 15) could be declared as const
--- Eff.
C++ 3rd Ed. item 3
l.c(15) : Info 830: Location cited in prior message
_
}
l.c(19) : Note 953: Variable 'romandigits' (line 16) could be declared
as const
--- Eff. C++ 3rd Ed. item 3
l.c(16) : Info 830: Location cited in prior message
--- Wrap-up for Module: l.c
Info 749: local enumeration constant 'values::I' (line 4, file l.c) not
referenced
l.c(4) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::V' (line 5, file l.c) not
referenced
l.c(5) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::X' (line 6, file l.c) not
referenced
l.c(6) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::L' (line 7, file l.c) not
referenced
l.c(7) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::C' (line 8, file l.c) not
referenced
l.c(8) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::D' (line 9, file l.c) not
referenced
l.c(9) : Info 830: Location cited in prior message
Info 749: local enumeration constant 'values::M' (line 10, file l.c) not
referenced
l.c(10) : Info 830: Location cited in prior message
---
output placed in _LINT.TMP
Keith Thompson
[...]
> You might choose to add -Wshaddow to your set of useful gcc options.
Typo: it's "-Wshadow".
--
Keith Thompson (The_Other_Keith) ks...@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"