data type

[aman]

is it true that c compiler automatically picks a variable as an
integer if we can't explicitly declare it at beginning of a program????

[santosh]

Re: data type

aman wrote:

is it true that c compiler automatically picks a variable as an
integer if we can't explicitly declare it at beginning of a program????

No. In C objects have to be declared before they are used.

[santosh]

Re: data type

santosh wrote:

aman wrote:
>

>is it true that c compiler automatically picks a variable as an
>integer if we can't explicitly declare it at beginning of a program????

>
No. In C objects have to be declared before they are used.

I should amend that for global objects it's true that the type defaults to
int when it's not specifically mentioned. However it's extremely bad
practise.

[Richard Heathfield]

Re: data type

santosh said:

aman wrote:
>

>is it true that c compiler automatically picks a variable as an
>integer if we can't explicitly declare it at beginning of a program????

>
No. In C objects have to be declared before they are used.

True in C99, but who's got that?

rjh@linux:~/scratchcat foo.c
#include <stdio.h>
foo(x)
{
return printf("%d\n", x);
}
int main(void)
{
foo(42);

return 0;
}

me@here:~/scratchmake
gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
-Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
foo.c:3: warning: return-type defaults to `int'
foo.c:3: warning: function declaration isn't a prototype
foo.c: In function `foo':
foo.c:3: warning: type of `x' defaults to `int'
gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
-Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
me@here:~/scratch./foo
42
me@here:~/scratch>

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Ben Pfaff]

Re: data type

Richard Heathfield <rjh@see.sig.in validwrites:

santosh said:
>

>aman wrote:
>>

>>is it true that c compiler automatically picks a variable as an
>>integer if we can't explicitly declare it at beginning of a program????

>>
>No. In C objects have to be declared before they are used.

>
True in C99, but who's got that?
>
rjh@linux:~/scratchcat foo.c
#include <stdio.h>
foo(x)

I believe that this is a declaration of x. (It is a declaration
that does not explicitly give the type of x.)

{
return printf("%d\n", x);
}

--
"You call this a *C* question? What the hell are you smoking?" --Kaz

[Richard Heathfield]

Re: data type

Ben Pfaff said:

Richard Heathfield <rjh@see.sig.in validwrites:
>

<snip>

>>
>rjh@linux:~/scratchcat foo.c
>#include <stdio.h>
>foo(x)

>
I believe that this is a declaration of x. (It is a declaration
that does not explicitly give the type of x.)

I, in turn, believe that this was roughly what the OP was getting at - i.e.
implicit int.

<snip>

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[jacob navia]

Re: data type

Richard Heathfield wrote:

santosh said:
>

>aman wrote:
>>

>>is it true that c compiler automatically picks a variable as an
>>integer if we can't explicitly declare it at beginning of a program????

>No. In C objects have to be declared before they are used.

>
True in C99, but who's got that?
>
rjh@linux:~/scratchcat foo.c
#include <stdio.h>
foo(x)
{
return printf("%d\n", x);
}
int main(void)
{
foo(42);
>
return 0;
}
>
me@here:~/scratchmake
gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
-Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
foo.c:3: warning: return-type defaults to `int'
foo.c:3: warning: function declaration isn't a prototype
foo.c: In function `foo':
foo.c:3: warning: type of `x' defaults to `int'
gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
-Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
me@here:~/scratch./foo
42
me@here:~/scratch>
>

heathfield is using the wrong compiler!

d:\lcc\test>typ e th1.c
#include <stdio.h>
foo(x)
{
return printf("%d\n", x);
}
int main(void)
{
foo(42);

return 0;
}

d:\lcc\test>lc th1.c
Warning th1.c: 2 no type specified. Defaulting to int
Warning th1.c: 8 Missing prototype for 'foo'
0 errors, 2 warnings

--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[Joachim Schmitz]

Re: data type

"jacob navia" <jacob@nospam.o rgschrieb im Newsbeitrag
news:47028ae8$0 $5103$ba4acef3@ news.orange.fr. ..

Richard Heathfield wrote:

>santosh said:
>>

>>aman wrote:
>>>
>>>is it true that c compiler automatically picks a variable as an
>>>integer if we can't explicitly declare it at beginning of a program????
>>No. In C objects have to be declared before they are used.

>>
>True in C99, but who's got that?
>>
>rjh@linux:~/scratchcat foo.c
>#include <stdio.h>
>foo(x)
>{
> return printf("%d\n", x);
>}
>int main(void)
>{
> foo(42);
>>
> return 0;
>}
> me@here:~/scratchmake
>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
> -Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
>foo.c:3: warning: return-type defaults to `int'
>foo.c:3: warning: function declaration isn't a prototype
>foo.c: In function `foo':
>foo.c:3: warning: type of `x' defaults to `int'
>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
> -Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
>me@here:~/scratch./foo
>42
>me@here:~/scratch>

>
heathfield is using the wrong compiler!
>
d:\lcc\test>typ e th1.c
#include <stdio.h>
foo(x)
{
return printf("%d\n", x);
}
int main(void)
{
foo(42);
>
return 0;
}
>
d:\lcc\test>lc th1.c
Warning th1.c: 2 no type specified. Defaulting to int
Warning th1.c: 8 Missing prototype for 'foo'
0 errors, 2 warnings

Why? He basically got the same warnings as you got. (When compiling, not
when linking, no surprise there)
Hmm, actually he got 3 warnings, your compiler produced 2

Bye, Jojo

[Ben Pfaff]

Re: data type

Richard Heathfield <rjh@see.sig.in validwrites:

Ben Pfaff said:
>

>Richard Heathfield <rjh@see.sig.in validwrites:

>>rjh@linux:~/scratchcat foo.c
>>#include <stdio.h>
>>foo(x)

>>
>I believe that this is a declaration of x. (It is a declaration
>that does not explicitly give the type of x.)

>
I, in turn, believe that this was roughly what the OP was getting at - i.e.
implicit int.

I can see that the OP's article could be interpreted that way.
It wasn't my interpretation.
--
"The fact that there is a holy war doesn't mean that one of the sides
doesn't suck - usually both do..."
--Alexander Viro

[santosh]

Re: data type

jacob navia wrote:

Richard Heathfield wrote:

>santosh said:
>>

>>aman wrote:
>>>
>>>is it true that c compiler automatically picks a variable as an
>>>integer if we can't explicitly declare it at beginning of a program????
>>No. In C objects have to be declared before they are used.

>>
>True in C99, but who's got that?
>>
>rjh@linux:~/scratchcat foo.c
>#include <stdio.h>
>foo(x)
>{
> return printf("%d\n", x);
>}
>int main(void)
>{
> foo(42);
>>
> return 0;
>}
>>
>me@here:~/scratchmake
>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
>-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
>-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
>-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>-Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
>foo.c:3: warning: return-type defaults to `int'
>foo.c:3: warning: function declaration isn't a prototype
>foo.c: In function `foo':
>foo.c:3: warning: type of `x' defaults to `int'
>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
>-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
>-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
>-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>-Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
>me@here:~/scratch./foo
>42
>me@here:~/scratch>
>>

>
heathfield is using the wrong compiler!

Why? gcc is emitting all the diagnostics that you'd expect and one more than
what lcc-win32 emits.

[jacob navia]

Re: data type

santosh wrote:

jacob navia wrote:
>

>Richard Heathfield wrote:

>>santosh said:
>>>
>>>aman wrote:
>>>>
>>>>is it true that c compiler automatically picks a variable as an
>>>>integer if we can't explicitly declare it at beginning of a program????
>>>No. In C objects have to be declared before they are used.
>>True in C99, but who's got that?
>>>
>>rjh@linux:~/scratchcat foo.c
>>#include <stdio.h>
>>foo(x)
>>{
>> return printf("%d\n", x);
>>}
>>int main(void)
>>{
>> foo(42);
>>>
>> return 0;
>>}
>>>
>>me@here:~/scratchmake
>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
>>-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
>>-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
>>-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>>-Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
>>foo.c:3: warning: return-type defaults to `int'
>>foo.c:3: warning: function declaration isn't a prototype
>>foo.c: In function `foo':
>>foo.c:3: warning: type of `x' defaults to `int'
>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align
>>-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes
>>-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef
>>-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>>-Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
>>me@here:~/scratch./foo
>>42
>>me@here:~/scratch>
>>>

>heathfield is using the wrong compiler!

>
Why? gcc is emitting all the diagnostics that you'd expect and one more than
what lcc-win32 emits.
>

Gosh!

I just did not see them in all the linking stuff!!

Excuse me. I will eat my hat now!
:-)


--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[jacob navia]

Re: data type

Joachim Schmitz wrote:

"jacob navia" <jacob@nospam.o rgschrieb im Newsbeitrag
news:47028ae8$0 $5103$ba4acef3@ news.orange.fr. ..

>Richard Heathfield wrote:

>>santosh said:
>>>
>>>aman wrote:
>>>>
>>>>is it true that c compiler automatically picks a variable as an
>>>>integer if we can't explicitly declare it at beginning of a program????
>>>No. In C objects have to be declared before they are used.
>>True in C99, but who's got that?
>>>
>>rjh@linux:~/scratchcat foo.c
>>#include <stdio.h>
>>foo(x)
>>{
>> return printf("%d\n", x);
>>}
>>int main(void)
>>{
>> foo(42);
>>>
>> return 0;
>>}
>> me@here:~/scratchmake
>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
>> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
>> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>> -Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
>>foo.c:3: warning: return-type defaults to `int'
>>foo.c:3: warning: function declaration isn't a prototype
>>foo.c: In function `foo':
>>foo.c:3: warning: type of `x' defaults to `int'
>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
>> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
>> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>> -Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
>>me@here:~/scratch./foo
>>42
>>me@here:~/scratch>

>heathfield is using the wrong compiler!
>>
>d:\lcc\test>ty pe th1.c
>#include <stdio.h>
>foo(x)
>{
> return printf("%d\n", x);
>}
>int main(void)
>{
> foo(42);
>>
> return 0;
>}
>>
>d:\lcc\test> lc th1.c
>Warning th1.c: 2 no type specified. Defaulting to int
>Warning th1.c: 8 Missing prototype for 'foo'
>0 errors, 2 warnings

Why? He basically got the same warnings as you got. (When compiling, not
when linking, no surprise there)
Hmm, actually he got 3 warnings, your compiler produced 2
>
Bye, Jojo
>
>

Sorry Joachim, I just did not see the warnings between all that
linking stuff.



--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[Joachim Schmitz]

Re: data type

"jacob navia" <jacob@nospam.o rgschrieb im Newsbeitrag
news:47028dfd$0 $27377$ba4acef3 @news.orange.fr ...

Joachim Schmitz wrote:

>"jacob navia" <jacob@nospam.o rgschrieb im Newsbeitrag
>news:47028ae8$ 0$5103$ba4acef3 @news.orange.fr ...

>>Richard Heathfield wrote:
>>>santosh said:
>>>>
>>>>aman wrote:
>>>>>
>>>>>is it true that c compiler automatically picks a variable as an
>>>>>integer if we can't explicitly declare it at beginning of a
>>>>>program??? ?
>>>>No. In C objects have to be declared before they are used.
>>>True in C99, but who's got that?
>>>>
>>>rjh@linux: ~/scratchcat foo.c
>>>#include <stdio.h>
>>>foo(x)
>>>{
>>> return printf("%d\n", x);
>>>}
>>>int main(void)
>>>{
>>> foo(42);
>>>>
>>> return 0;
>>>}
>>> me@here:~/scratchmake
>>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
>>> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
>>> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>>> -Wno-conversion -ffloat-store -O2 -g -pg -c -o foo.o foo.c
>>>foo.c:3: warning: return-type defaults to `int'
>>>foo.c:3: warning: function declaration isn't a prototype
>>>foo.c: In function `foo':
>>>foo.c:3: warning: type of `x' defaults to `int'
>>>gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -Wpointer-arith
>>> -Wbad-function-cast -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
>>> -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings
>>> -Wno-conversion -ffloat-store -O2 -g -pg -o foo foo.o -lm
>>>me@here:~/scratch./foo
>>>42
>>>me@here:~/scratch>
>>heathfield is using the wrong compiler!
>>>
>>d:\lcc\test>t ype th1.c
>>#include <stdio.h>
>>foo(x)
>>{
>> return printf("%d\n", x);
>>}
>>int main(void)
>>{
>> foo(42);
>>>
>> return 0;
>>}
>>>
>>d:\lcc\test>l c th1.c
>>Warning th1.c: 2 no type specified. Defaulting to int
>>Warning th1.c: 8 Missing prototype for 'foo'
>>0 errors, 2 warnings

>Why? He basically got the same warnings as you got. (When compiling, not
>when linking, no surprise there)
>Hmm, actually he got 3 warnings, your compiler produced 2
>>
>Bye, Jojo

>
Sorry Joachim, I just did not see the warnings between all that
linking stuff.

It's not me you own an apology...

Bye, Jojo

[Flash Gordon]

Re: data type

Richard Heathfield wrote, On 02/10/07 19:01:

Ben Pfaff said:
>

>Richard Heathfield <rjh@see.sig.in validwrites:
>>

<snip>

>>rjh@linux:~/scratchcat foo.c
>>#include <stdio.h>
>>foo(x)

>I believe that this is a declaration of x. (It is a declaration
>that does not explicitly give the type of x.)

>
I, in turn, believe that this was roughly what the OP was getting at - i.e.
implicit int.

The OP should note that there are ways of defining a variable that avoid
explicitly providing a type. E.g.
{
auto i;
}
C99 has removed implicit int from the language, so I believe the above
is not valid C99.
--
Flash Gordon

[Keith Thompson]

Re: data type

santosh <santosh.k83@gm ail.comwrites:

santosh wrote:

>aman wrote:
>>

>>is it true that c compiler automatically picks a variable as an
>>integer if we can't explicitly declare it at beginning of a program????

>>
>No. In C objects have to be declared before they are used.

>
I should amend that for global objects it's true that the type defaults to
int when it's not specifically mentioned. However it's extremely bad
practise.

There isn't really a distinction between "global" and other objects.
C90 allows implicit int in a number of contexts. For example:

static x; /* x is int by default */
auto y; /* y is int by default; allowed only inside a function */
register z; /* z is int by default; allowed only inside a function */

Generally an object (variable) declaration requires *either* a storage
class *or* a type.

But declaring a variable without specifying its type is considered
poor style, and the newer C99 standard forbids it.

You can do it, but you shouldn't.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"