Typedef shadowing?

[codenamezero]

I am using C, there is no dynamic array. So i tried this and it worked... but want to know if this can be platform independent so i can actually use this across any platform.

typedef struct {
uint16_t n;
uint32_t m;
char filename[1024];     
} MY_TYPEDEF

// for no padding binary output to file
#pragma pack(1) 
typedef struct {
uint16_t n;
uint32_t m;
char filename[];         // empty array
} MY_TYPEDEF_NO_PACK
#pragma pack(0) 

Now, when i output it, i need to copy over to the other structure without padding before i do the binary output. However, i cannot do stuff like:

MY_TYPEDEF_NO_PACK   tmp_struct;
...
fwrite(tmp_struct, 1, sizeof(MY_TYPEDEF_NO_PACK), fp);

because i don't know how big my filename will be...

BUT, if i redefine the typedef within my other output function like this:

#pragma pack(1) 
typedef struct {
uint16_t n;
uint32_t m;
 char filename[strlen(data->filename)];
} MY_TYPEDEF_NO_PACK
#pragma pack(0) 
 
MY_TYPEDEF_NO_PACK   tmp_struct;
...
fwrite(tmp_struct, 1, sizeof(MY_TYPEDEF_NO_PACK), fp);

Then it will show the correct size lol...
It works, but i want to know if this can be ported to other platform.

THERE WERE NO ERROR or WARNINGS from the gcc... even with -W

Any thought?

[JosAH]

char filename[strlen(data->filename)];

THERE WERE NO ERROR or WARNINGS from the gcc... even with -W

Any thought?

Yep; that most definitely is a gnu extension. Didn't gcc warn even with a -Wall
flag set?

kind regards,

Jos

[codenamezero]

Nope, zero warning.
Have you done this "hack" before?

Well it will give warning IF i use it in my header file.
But since i already have it defined in my header with an EMPTY ARRAY, so i think it didn't complain when the compiler sees it the second time inside local function.

char filename[]; 

Was defined in a header file.

char filename[strlen(data.filename)];

Was re-defined in another function, sort act like a local typedef.

[codenamezero]

Ah on Solaris it would report expected constant. So i guess it doesn't work cross platform hehe...