"Incomplete type" and "redefinition" errors in gcc

"Incomplete type" and "redefinition" errors in gcc

[Ashutosh Dixit]

Hi,

If I compile the following simple C code with gcc:
________________try.c________________________

typedef enum VIDF VIDF;
typedef unsigned int U32;
typedef unsigned int U32;

typedef struct VIDR
{
  VIDF VidF;
  U32  width;
} VIDR;

typedef enum VIDF
{
  aVIDF,
  bVIDF
} VIDF;

int main( void )
{
  return 0;
}
____________________________________________

I get the following errors:

bash-2.05b$ gcc try.c
try.c:3: error: redefinition of `U32'
try.c:2: error: `U32' previously declared here
try.c:7: error: field `VidF' has incomplete type
try.c:15: error: redefinition of `VIDF'
try.c:1: error: `VIDF' previously declared here
______________________________________________

I would have thought that the code would compile
without errors. Are these bugs or features of gcc (or
of the C language standard) and are there any options
to make these errors disappear?

The preceding is only sample code. In the real code
which I am trying to compile, making changes to take
care of these errors will be very cumbersome.
I am using gcc 3.3.1 on Cygwin.

Thanks very much for your help.

Ashutosh


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Re: "Incomplete type" and "redefinition" errors in gcc

[Richard Earnshaw]

> Hi,
> 
> If I compile the following simple C code with gcc:
> ________________try.c________________________
> 
> typedef enum VIDF VIDF;
> typedef unsigned int U32;
> typedef unsigned int U32;
> 
> typedef struct VIDR
> {
>   VIDF VidF;
>   U32  width;
> } VIDR;
> 
> typedef enum VIDF
> {
>   aVIDF,
>   bVIDF
> } VIDF;
> 
> int main( void )
> {
>   return 0;
> }
> ____________________________________________
> 
> I get the following errors:
> 
> bash-2.05b$ gcc try.c
> try.c:3: error: redefinition of `U32'
> try.c:2: error: `U32' previously declared here
> try.c:7: error: field `VidF' has incomplete type
> try.c:15: error: redefinition of `VIDF'
> try.c:1: error: `VIDF' previously declared here

All of these diagnostics are correct.   You can't repeat typedefs, and you 
can't instantiate a forward declaration of an enum.

R.

Re: "Incomplete type" and "redefinition" errors in gcc

[Gabriel Dos Reis]

Richard Earnshaw <rearnsha@arm.com> writes:

| > Hi,
| > 
| > If I compile the following simple C code with gcc:
| > ________________try.c________________________
| > 
| > typedef enum VIDF VIDF;
| > typedef unsigned int U32;
| > typedef unsigned int U32;

[...]

| All of these diagnostics are correct.   You can't repeat typedefs, and you 
| can't instantiate a forward declaration of an enum.

I see the original poster was mentioning C.  However, I just wanted to
add that in C++, it is permitted to repeat a typedef declaration
provided it binds the same tokens.  The enum forward declaration
restrictions are same in both languages.

-- Gaby

Re: "Incomplete type" and "redefinition" errors in gcc

[Ashutosh Dixit]

Richard/Gabriel,

Thanks very much for replying. The program does
compile under MSVC.NET - I guess we should consider
that as non-standard MS extensions to the language...

Thanks,

Ashutosh


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"Incomplete type" and "redefinition" errors in gcc

[Ashutosh Dixit]

Hi,

If I compile the following simple C code with gcc:
________________try.c________________________

typedef enum VIDF VIDF;
typedef unsigned int U32;
typedef unsigned int U32;

typedef struct VIDR
{
  VIDF VidF;
  U32  width;
} VIDR;

typedef enum VIDF
{
  aVIDF,
  bVIDF
} VIDF;

int main( void )
{
  return 0;
}
____________________________________________

I get the following errors:

bash-2.05b$ gcc try.c
try.c:3: error: redefinition of `U32'
try.c:2: error: `U32' previously declared here
try.c:7: error: field `VidF' has incomplete type
try.c:15: error: redefinition of `VIDF'
try.c:1: error: `VIDF' previously declared here
______________________________________________

I would have thought that the code would compile
without errors. Are these bugs or features of gcc and
are there any options to make these errors disappear?

The preceding is only sample code. In the real code
which I am trying to compile, making changes to take
care of these errors will be very cumbersome.
I am using gcc 3.3.1 on Cygwin.

Thanks very much for your help.

Ash


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