void func () returning value?

[Yevgen Muntyan]

Hey,

Consider the following code:

void func (void)
{
}

void func2 (void)
{
return func ();
}

gcc -pedantic says the following:

muntyan@munt10:/tmp$ gcc -pedantic -c file.c
file.c: In function ‘func2’:
file.c:7: warning: ‘return’ with a value, in function returning void

If I recall correctly, compiler in some Microsoft Visual Studio version
told me the same thing. So, is this a compiler bug (feature), or is this
"return func ();" invalid in standard C?

Thanks,
Yevgen

[Harald van Dijk]

Re: void func () returning value?

Yevgen Muntyan wrote:

Hey,
>
Consider the following code:
>
void func (void)
{
}
>
void func2 (void)
{
return func ();
}
>
gcc -pedantic says the following:
>
muntyan@munt10:/tmp$ gcc -pedantic -c file.c
file.c: In function ‘func2’:
file.c:7: warning: ‘return’ with a value, in function returning void
>
If I recall correctly, compiler in some Microsoft Visual Studio version
told me the same thing. So, is this a compiler bug (feature), or is this
"return func ();" invalid in standard C?

It's invalid in standard C. Perhaps you're thinking of C++, where it is
allowed?

[Nick Keighley]

Re: void func () returning value?

Harald van Dijk wrote:

Yevgen Muntyan wrote:

Consider the following code:

void func (void)
{
}

void func2 (void)
{
return func ();
}

gcc -pedantic says the following:

muntyan@munt10:/tmp$ gcc -pedantic -c file.c
file.c: In function ‘func2’:
file.c:7: warning: ‘return’ with a value, in function returning void

If I recall correctly, compiler in some Microsoft Visual Studio version
told me the same thing. So, is this a compiler bug (feature), or is this
"return func ();" invalid in standard C?

>
It's invalid in standard C. Perhaps you're thinking of C++, where it is
allowed?

since when has it been valid for a void function to return a value, in
either C or C++?


--
Nick Keighley

[Greg]

Re: void func () returning value?


Nick Keighley wrote:

Harald van Dijk wrote:

Yevgen Muntyan wrote:

>

Consider the following code:
>
void func (void)
{
}
>
void func2 (void)
{
return func ();
}
>
gcc -pedantic says the following:
>
muntyan@munt10:/tmp$ gcc -pedantic -c file.c
file.c: In function ‘func2’:
file.c:7: warning: ‘return’ with a value, in functionreturni ng void
>
If I recall correctly, compiler in some Microsoft Visual Studio version
told me the same thing. So, is this a compiler bug (feature), or is this
"return func ();" invalid in standard C?

It's invalid in standard C. Perhaps you're thinking of C++, where it is
allowed?

>
since when has it been valid for a void function to return a value, in
either C or C++?

It's not legal in C++ for a "return" statement of a void function to
return a value [§6.6.3]. The above program is nonetheless OK since it
is legal in C++ for a return statement in a void function to have a
(cv) void type expression - as in this case, the return expression is
simply a call to another void function.

Greg

[Risto Lankinen]

Re: void func () returning value?


"Nick Keighley" <nick_keighley_ nospam@hotmail. comwrote in message
news:1161157294 .584254.312760@ h48g2000cwc.goo glegroups.com.. .

>since when has it been valid for a void function to return a value, in
>either C or C++?

A void function can "return" an expression whose type is void . This
is to facilitate templates such as...

template <typename TT func() { return static_cast<T>( expr); }

.... to be instantiable also for T=void.

- Risto -

--
Nick Keighley

[Yevgen Muntyan]

Re: void func () returning value?

Harald van Dijk wrote:

Yevgen Muntyan wrote:
>

>>Hey,
>>
>>Consider the following code:
>>
>>void func (void)
>>{
>>}
>>
>>void func2 (void)
>>{
> return func ();
>>}
>>
>>gcc -pedantic says the following:
>>
>>muntyan@munt1 0:/tmp$ gcc -pedantic -c file.c
>>file.c: In function ‘func2’:
>>file.c:7: warning: ‘return’ with a value, in function returning void
>>
>>If I recall correctly, compiler in some Microsoft Visual Studio version
>>told me the same thing. So, is this a compiler bug (feature), or is this
>>"return func ();" invalid in standard C?

>
>
It's invalid in standard C. Perhaps you're thinking of C++, where it is
allowed?

I am sure I was thinking about C :)
After comparing C and C++ standards it looks like it's a useful C++
feature which wasn't backported to C standard. I thought it was
natural to do 'return func()' for func() returning nothing, but
now I'm curious if there are other languages where it's valid
(I could swear it's so in one of languages I know and where function
can really return nothing, but it's not the case).

Best regards,
Yevgen

[mark_bluemel@pobox.com]

Re: void func () returning value?


Yevgen Muntyan wrote:

After comparing C and C++ standards it looks like it's a useful C++
feature which wasn't backported to C standard.

For some value of "useful"...

BTW: are you implying that C is, or should be, a subset of C++?
That would, I suspect, be "fighting talk" :-)

I thought it was
natural to do 'return func()' for func() returning nothing,

I thought it was unnatural - funny how people's interpretation of
"natural" varies...

[Yevgen Muntyan]

Re: void func () returning value?

mark_bluemel@po box.com wrote:

Yevgen Muntyan wrote:
>
>

>>After comparing C and C++ standards it looks like it's a useful C++
>>feature which wasn't backported to C standard.

>
>
For some value of "useful"...

void foo (void)
{
...
for (i = 0; i < 42; ++i)
if (bar (i))
return simple_foo (i);
real_foo_here() ;
}

Using two statements (function call and return) makes it lot
uglier for me - bunch of curly brackets added. Not a real problem,
of course, but I find "return void_func();" very nice.

BTW: are you implying that C is, or should be, a subset of C++?
That would, I suspect, be "fighting talk" :-)

No, of course no, I think that C++ is a superset of C ;)
Seriously speaking, // comments are a (useful, I think) C++
feature "backported " to C, aren't they? I absolutely didn't mean
"C sucks because C++...." or "C++ is so much nicer because..."

Best regards,
Yevgen

[mark_bluemel@pobox.com]

Re: void func () returning value?


Yevgen Muntyan wrote:

void foo (void)
{
...
for (i = 0; i < 42; ++i)
if (bar (i))
return simple_foo (i);
real_foo_here() ;
}
>
Using two statements (function call and return) makes it lot
uglier for me - bunch of curly brackets added. Not a real problem,
of course, but I find "return void_func();" very nice.

As a predominantly maintenance programmer, I would immediately have
changed your code to

void foo (void)
{
...
for (i = 0; i < 42; ++i) {
if (bar (i)) {
return simple_foo (i);
}
}
real_foo_here() ;
}

for starters, so splitting function call and return into two lines is
not a big overhead. Leaving braces out is a recipe for future bugs
IMHO....

I stick to my opinion that "void foo()" means that "foo()" doesn't
return anything, so combining an arbitrary call to a void function with
the return is fairly stupid. If you wanted to call something and ignore
its result would you do (for example) 'return (void)printf("M y Dog Has
Fleas\n");' ?

As for "//" for comments, I'm rather inclined to prefer "/* ... */" but
that's a personal thing, I guess

[Fred Kleinschmidt]

Re: void func () returning value?


<mark_bluemel@p obox.comwrote in message
news:1161178776 .881285.207080@ m7g2000cwm.goog legroups.com...

>
Yevgen Muntyan wrote:
>

>void foo (void)
>{
> ...
> for (i = 0; i < 42; ++i)
> if (bar (i))
> return simple_foo (i);
> real_foo_here() ;
>}
>>
>Using two statements (function call and return) makes it lot
>uglier for me - bunch of curly brackets added. Not a real problem,
>of course, but I find "return void_func();" very nice.

>
As a predominantly maintenance programmer, I would immediately have
changed your code to
>
void foo (void)
{
...
for (i = 0; i < 42; ++i) {
if (bar (i)) {
return simple_foo (i);
}
}
real_foo_here() ;
}
>
for starters, so splitting function call and return into two lines is
not a big overhead. Leaving braces out is a recipe for future bugs
IMHO....
>
I stick to my opinion that "void foo()" means that "foo()" doesn't
return anything, so combining an arbitrary call to a void function with
the return is fairly stupid. If you wanted to call something and ignore
its result would you do (for example) 'return (void)printf("M y Dog Has
Fleas\n");' ?
>
As for "//" for comments, I'm rather inclined to prefer "/* ... */" but
that's a personal thing, I guess
>

I would have changed it to:

void foo (void)
{
...
for (i = 0; i < 42; ++i) {
if (bar (i)) {
simple_foo (i);
return;
}
}
real_foo_here() ;
}

Think what would happen if simple_foo() werre changed
to return a value (an error code, of perhaps something else
that foo() is not interested in). If you instead used
return simple_foo(i)
then suddenly the program would not compile.

Now, this may or may not be a reasonable thing.
The compile error would certainly warn you that
perhaps you should pay attention to the return value
of the modified simple_foo() function.
--
Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project

[Al Balmer]

Re: void func () returning value?

On Wed, 18 Oct 2006 09:43:18 GMT, Yevgen Muntyan
<muntyan.remove this@tamu.eduwr ote:

>Harald van D?k wrote:

>Yevgen Muntyan wrote:
>>

>>>Hey,
>>>
>>>Consider the following code:
>>>
>>>void func (void)
>>>{
>>>}
>>>
>>>void func2 (void)
>>>{
>> return func ();
>>>}
>>>
>>>gcc -pedantic says the following:
>>>
>>>muntyan@munt 10:/tmp$ gcc -pedantic -c file.c
>>>file.c: In function ‘func2’:
>>>file.c:7: warning: ‘return’ with a value, in function returning void
>>>
>>>If I recall correctly, compiler in some Microsoft Visual Studio version
>>>told me the same thing. So, is this a compiler bug (feature), or is this
>>>"return func ();" invalid in standard C?

>>
>>
>It's invalid in standard C. Perhaps you're thinking of C++, where it is
>allowed?

>
>I am sure I was thinking about C :)
>After comparing C and C++ standards it looks like it's a useful C++
>feature which wasn't backported to C standard.

In C, it's a trivial transformation to

func();
return;

What's useful about it? (Aside from possible use in obfuscation.)

I thought it was
>natural to do 'return func()' for func() returning nothing, but
>now I'm curious if there are other languages where it's valid
>(I could swear it's so in one of languages I know and where function
>can really return nothing, but it's not the case).
>
>Best regards,
>Yevgen

--
Al Balmer
Sun City, AZ

[Richard]

Re: void func () returning value?

"Harald van Dijk" <truedfx@gmail. comwrites:

Yevgen Muntyan wrote:

>Hey,
>>
>Consider the following code:
>>
>void func (void)
>{
>}
>>
>void func2 (void)
>{
> return func ();
>}
>>
>gcc -pedantic says the following:
>>
>muntyan@munt10 :/tmp$ gcc -pedantic -c file.c
>file.c: In function ‘func2’:
>file.c:7: warning: ‘return’ with a value, in function returning void
>>
>If I recall correctly, compiler in some Microsoft Visual Studio version
>told me the same thing. So, is this a compiler bug (feature), or is this
>"return func ();" invalid in standard C?

>
It's invalid in standard C. Perhaps you're thinking of C++, where it is
allowed?
>

It is also bad practice IMO.

When reading the code you would immediately assume that func()
is returning a required value.

I have also found in years of modifying large legacy code bases that
"return func()" is not as easy to monitor and debug as "rc= func();
return rc;". Admittedly a personal preference built up from my own
experiences.

[Elijah Cardon]

Re: void func () returning value?


"Richard" <rgrdev@gmail.c omwrote in message
news:87ac3tab01 .fsf@gmail.com. ..

"Harald van D?k" <truedfx@gmail. comwrites:
>

>Yevgen Muntyan wrote:

>>Hey,
>>>
>>Consider the following code:
>>>
>>void func (void)
>>{
>>}
>>>
>>void func2 (void)
>>{
>> return func ();
>>}
>>>
>>gcc -pedantic says the following:
>>>
>>muntyan@munt1 0:/tmp$ gcc -pedantic -c file.c
>>file.c: In function 'func2':
>>file.c:7: warning: 'return' with a value, in function returning void
>>>
>>If I recall correctly, compiler in some Microsoft Visual Studio version
>>told me the same thing. So, is this a compiler bug (feature), or is this
>>"return func ();" invalid in standard C?

>>
>It's invalid in standard C. Perhaps you're thinking of C++, where it is
>allowed?
>>

>
It is also bad practice IMO.
>
When reading the code you would immediately assume that func()
is returning a required value.
>
I have also found in years of modifying large legacy code bases that
"return func()" is not as easy to monitor and debug as "rc= func();
return rc;". Admittedly a personal preference built up from my own
experiences.

Why do people TRY to find bad logic scenarios with the C Programming
Language. You have two void functions and try to return a call to the first
in the second. If a compiler didn't scream, I would. EC

[Yevgen Muntyan]

Re: void func () returning value?

Fred Kleinschmidt wrote:

<mark_bluemel@p obox.comwrote in message
news:1161178776 .881285.207080@ m7g2000cwm.goog legroups.com...
>

>>Yevgen Muntyan wrote:
>>
>>

>>>void foo (void)
>>>{
>> ...
>> for (i = 0; i < 42; ++i)
>> if (bar (i))
>> return simple_foo (i);
>> real_foo_here() ;
>>>}
>>>
>>>Using two statements (function call and return) makes it lot
>>>uglier for me - bunch of curly brackets added. Not a real problem,
>>>of course, but I find "return void_func();" very nice.

>>
>>As a predominantly maintenance programmer, I would immediately have
>>changed your code to
>>
>>void foo (void)
>>{
> ...
> for (i = 0; i < 42; ++i) {
> if (bar (i)) {
> return simple_foo (i);
> }
> }
> real_foo_here() ;
>>}
>>
>>for starters, so splitting function call and return into two lines is
>>not a big overhead. Leaving braces out is a recipe for future bugs
>>IMHO....
>>
>>I stick to my opinion that "void foo()" means that "foo()" doesn't
>>return anything, so combining an arbitrary call to a void function with
>>the return is fairly stupid. If you wanted to call something and ignore
>>its result would you do (for example) 'return (void)printf("M y Dog Has
>>Fleas\n");' ?
>>
>>As for "//" for comments, I'm rather inclined to prefer "/* ... */" but
>>that's a personal thing, I guess
>>

>
>
I would have changed it to:
>
void foo (void)
{
...
for (i = 0; i < 42; ++i) {
if (bar (i)) {
simple_foo (i);
return;
}
}
real_foo_here() ;
}
>
Think what would happen if simple_foo() werre changed
to return a value (an error code, of perhaps something else
that foo() is not interested in). If you instead used
return simple_foo(i)
then suddenly the program would not compile.

Yes, exactly. Compiler will complain if either foo or simple_foo
change return value from void to something. And it is a really
good thing.

Regards,
Yevgen

[Yevgen Muntyan]

Re: void func () returning value?

mark_bluemel@po box.com wrote:

Yevgen Muntyan wrote:
>
>

>>void foo (void)
>>{
> ...
> for (i = 0; i < 42; ++i)
> if (bar (i))
> return simple_foo (i);
> real_foo_here() ;
>>}
>>
>>Using two statements (function call and return) makes it lot
>>uglier for me - bunch of curly brackets added. Not a real problem,
>>of course, but I find "return void_func();" very nice.

>
>
As a predominantly maintenance programmer, I would immediately have
changed your code to
>
void foo (void)
{
...
for (i = 0; i < 42; ++i) {
if (bar (i)) {
return simple_foo (i);
}
}
real_foo_here() ;
}
>
for starters, so splitting function call and return into two lines is
not a big overhead. Leaving braces out is a recipe for future bugs
IMHO....
>

If I got this piece of code (with split return statement), I would
change it to:

void foo (void)
{
...
for (i = 0; i < 42; ++i)
{
if (bar (i))
{
simple_foo ();
return;
}
}
real_foo_here() ;
}

And *here* brackets are no good if you can do without them at all.
A nitpick/rationale: your coding style forces you to always use brackets
since you can't clearly see if there is an opening bracket, so closing
bracket alone is easily lost, and "Leaving braces out is a recipe for
future bugs". In mine, I can easily *see* that I need to add brackets if
I suddenly add a statement. Hope it will not start yet another flame
war on coding style ;)

I stick to my opinion that "void foo()" means that "foo()" doesn't
return anything, so combining an arbitrary call to a void function with
the return is fairly stupid. If you wanted to call something and ignore
its result would you do (for example) 'return (void)printf("M y Dog Has
Fleas\n");' ?

No, I wouldn't. Because this cast hides return value, so it's dangerous.
In case with void-void compiler will warn me if some function changes
return type, so I'm safe.

>
As for "//" for comments, I'm rather inclined to prefer "/* ... */" but
that's a personal thing, I guess

Sure it is.

Best regards,
Yevgen