invalid operands to binary == or wrong type argument to unary exclamation mark

[Sheldon]

Hi Everyone,

I have defined a function:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv);

and in the code:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv) {

snip

if(hdfdata != NULL) free(hdfdata);
return retv;
fail:
if(hdfdata != NULL) free(hdfdata);
exit(EXIT_FAILURE);
}

called the function like this:

if (arrFromHdfNode(nodelist,retv) == NULL) {
fprintf(stderr,"Failed getting data\n");
goto fail;

or like this

if (!(arrFromHdfNode(nodelist,retv))) {
fprintf(stderr,"Failed getting data\n");
goto fail;

The functions should return a struct or exit(EXIT_FAILURE) if
something went wrong.

For the first call I got the error:
error: invalid operands to binary ==
and for the second I got:
error: wrong type argument to unary exclamation mark

Can someone point me in the right direction? What is going on here?

Thanks in advance,
/S

[santosh]

On Tuesday 06 Nov 2007 3:45 pm Sheldon <sh******@gmail.comwrote in
article <11**********************@o38g2000hse.googlegroups .com>:

Hi Everyone,

I have defined a function:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv);

and in the code:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv) {

snip

if(hdfdata != NULL) free(hdfdata);
return retv;
fail:
if(hdfdata != NULL) free(hdfdata);
exit(EXIT_FAILURE);
}

called the function like this:

if (arrFromHdfNode(nodelist,retv) == NULL) {
fprintf(stderr,"Failed getting data\n");
goto fail;

or like this

if (!(arrFromHdfNode(nodelist,retv))) {
fprintf(stderr,"Failed getting data\n");
goto fail;

The functions should return a struct or exit(EXIT_FAILURE) if
something went wrong.

For the first call I got the error:
error: invalid operands to binary ==
and for the second I got:
error: wrong type argument to unary exclamation mark

Can someone point me in the right direction? What is going on here?

The function is defined as returning a struct Transient type object.
NULL is a pointer constant value. Both are not directly comparable. One
possibility is for the function to return a pointer to struct Transient
and return a null pointer value on error.

Similarly the ! operand accepts only a scalar type. A struct object is
not a scalar type. Again returning a pointer to that struct type would
solve this problem.

[Richard Heathfield]

Sheldon said:

Hi Everyone,

I have defined a function:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv);

and in the code:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv) {

snip

if(hdfdata != NULL) free(hdfdata);
return retv;

That's an unconditional return, and you're not in a loop or anything like
that. So everything from here to the end of that function is unreachable
code.

fail:

You don't use this.

if(hdfdata != NULL) free(hdfdata);
exit(EXIT_FAILURE);
}

called the function like this:

if (arrFromHdfNode(nodelist,retv) == NULL) {

But arrFromHdfNode returns a struct, not a pointer. C doesn't allow you to
use the == operator to compare structs, so you can't have a struct as one
of the operands, and the value returned by arrFromHdfNode(nodelist, retv)
has struct type, and that's why you're getting your error.

fprintf(stderr,"Failed getting data\n");
goto fail;

You're trying to use goto to jump from one function to a label in another
function. Again, this is against the rules of C.
--
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

[Sheldon]

On 6 Nov, 11:25, Richard Heathfield <[e-mail]:

Sheldon said:

Hi Everyone,

I have defined a function:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv);

and in the code:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv) {

snip

if(hdfdata != NULL) free(hdfdata);
return retv;

That's an unconditional return, and you're not in a loop or anything like
that. So everything from here to the end of that function is unreachable
code.

fail:

You don't use this.

if(hdfdata != NULL) free(hdfdata);
exit(EXIT_FAILURE);
}

called the function like this:

if (arrFromHdfNode(nodelist,retv) == NULL) {

But arrFromHdfNode returns a struct, not a pointer. C doesn't allow you to
use the == operator to compare structs, so you can't have a struct asone
of the operands, and the value returned by arrFromHdfNode(nodelist, retv)
has struct type, and that's why you're getting your error.

fprintf(stderr,"Failed getting data\n");
goto fail;

You're trying to use goto to jump from one function to a label in another
function. Again, this is against the rules of C.

--
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- Dölj citerad text -

- Visa citerad text -

Thanks! Will redo the code accordingly.

/S

[Sheldon]

On 6 Nov, 11:22, santosh <[e-mail]:

On Tuesday 06 Nov 2007 3:45 pm Sheldon <[e-mail] in
article <[e-mail] .com>:

Hi Everyone,

I have defined a function:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv);

and in the code:

struct Transient arrFromHdfNode(HL_NodeList *nodelist, struct
Transient retv) {

snip

if(hdfdata != NULL) free(hdfdata);
return retv;
fail:
if(hdfdata != NULL) free(hdfdata);
exit(EXIT_FAILURE);
}

called the function like this:

if (arrFromHdfNode(nodelist,retv) == NULL) {
fprintf(stderr,"Failed getting data\n");
goto fail;

or like this

if (!(arrFromHdfNode(nodelist,retv))) {
fprintf(stderr,"Failed getting data\n");
goto fail;

The functions should return a struct or exit(EXIT_FAILURE) if
something went wrong.

For the first call I got the error:
error: invalid operands to binary ==
and for the second I got:
error: wrong type argument to unary exclamation mark

Can someone point me in the right direction? What is going on here?

The function is defined as returning a struct Transient type object.
NULL is a pointer constant value. Both are not directly comparable. One
possibility is for the function to return a pointer to struct Transient
and return a null pointer value on error.

Similarly the ! operand accepts only a scalar type. A struct object is
not a scalar type. Again returning a pointer to that struct type would
solve this problem.- Dölj citerad text -

- Visa citerad text -

Thanks! Will redo the code accordingly.

/S

[Willem]

Richard wrote:
) Sheldon said:
)snip
)>
) if(hdfdata != NULL) free(hdfdata);
) return retv;
)
) That's an unconditional return, and you're not in a loop or anything like
) that. So everything from here to the end of that function is unreachable
) code.
)
) fail:
)
) You don't use this.

Isn't that right there a label you can goto ?

) if(hdfdata != NULL) free(hdfdata);
) exit(EXIT_FAILURE);
)}
SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT