Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
However, why doesn't this extend to a global variable which isn't
declared? The compiler gives as error immediately...
Thanks in advance!!!
6  1461 
Rahul wrote:
Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
This is surely not good practice and is maintened for backward
compatibility only.
However, why doesn't this extend to a global variable which isn't
declared? The compiler gives as error immediately...
Better that that than at link time isn't it?
Thanks in advance!!!
--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique http://www.cs.virginia.edu/~lcc-win32
On Jan 5, 3:42 pm, jacob navia <ja...@nospam.c omwrote:
Rahul wrote:
Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
This is surely not good practice and is maintened for backward
compatibility only.
Do you mean resolution during link time?
and backward compatibility with what?
Rahul wrote:
On Jan 5, 3:42 pm, jacob navia <ja...@nospam.c omwrote:
>Rahul wrote:
>>Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
This is surely not good practice and is maintened for backward
compatibilit y only.
Do you mean resolution during link time?
and backward compatibility with what?
I mean
<quote>
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
<end quote>
Implicit int is an obsolescent feature.
--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique http://www.cs.virginia.edu/~lcc-win32
jacob navia wrote, On 05/01/08 19:05:
Rahul wrote:
>On Jan 5, 3:42 pm, jacob navia <ja...@nospam.c omwrote:
>>Rahul wrote:
Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
This is surely not good practice and is maintened for backward
compatibili ty only.
Do you mean resolution during link time?
and backward compatibility with what?
I mean
<quote>
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
<end quote>
Implicit int is an obsolescent feature.
In the latest version of the standard it is not obsolescent (which means
that it is still present but may be removed) it is completely gone from
the language. In the previous standards I believe it was included for
backwards compatibility with pre-standard code.
--
Flash Gordon
On Sat, 5 Jan 2008 02:35:41 -0800 (PST), Rahul <sa*****@yahoo. co.in>
wrote in comp.lang.c:
Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
Actually, that "feature" was removed from the language in the 1999
version, and all later versions of the C standard. So don't write
code like that anymore.
However, why doesn't this extend to a global variable which isn't
declared? The compiler gives as error immediately...
Why should it? The call of functions without a declaration should
never have been in the language in the first place.
--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++ http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html
"Rahul" <sa*****@yahoo. co.inwrote in message
news:50******** *************** ***********@i72 g2000hsd.google groups.com...
Hi Everyone,
when a call to a function is done in a file and if the function isn't
defined, compiler just assumes that it would return a int and that the
definition would be available at some other compilation unit which
should be given to the linker to generate the executable file.
However, why doesn't this extend to a global variable which isn't
declared? The compiler gives as error immediately...
Thanks in advance!!!
that error may have crept into the old C because the compiler could do some
sort of
code generation for a function call, but not for variables.
if function f() is not defined (and not declared in its prototype form -
this is important), the
compiler assumes the form "int f()" , which to very likely to be incorrect,
because the actual definition may be
say void f(int,float). The compiler has generated code at the point of call
for a function with "int" return and
no arguments. Whereras the function expects an int and float (maybe on
stack, or in registers), but does not return anything.
A runtime disaster, no doubt but mericifully detected by linker
In contrast, what code can the compiler generate for an undeclared variable
? None, because the compiler not
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