Initializer element is not constant

Initializer element is not constant

[Scott]

Hi,

It has been a LONG TIME since I've done any programming in C. I have
two old programs still in use which were developed on msdos, using the
"Mark Williams Let's C" compiler. We're talking 1980's stuff here.

Anyway, I thought to try to port them to linux. Can anyone tell me
what I'm doing wrong?

Here are the relevant portions of indatax.c:

char *namectrl = NULL;
char *name1 = NULL;
char *name2 = NULL;

typedef struct {
	char *var;	/* destination for storage of the data */
	size_t len;	/* max len of the data */
	char *(*xlat)();	/* translation routine */
} DATUM;

DATUM recip_data[] = {
{  namectrl, NAMECTRL_LEN, make_upper },
{  name1, NAME1_LEN, make_upper },
{  name2, NAME2_LEN, make_upper },
[...]

And these are the errors...

indatax.c:124: initializer element is not constant
indatax.c:124: (near initialization for `recip_data[0].var')
indatax.c:125: initializer element is not constant
indatax.c:125: (near initialization for `recip_data[1].var')
indatax.c:126: initializer element is not constant
indatax.c:126: (near initialization for `recip_data[2].var')
[...]

gcc version 2.95.3

Thanks,

Scott Swanson
Pendroy, Montana

Re: Initializer element is not constant

[Ron Michael Khu]

Hi,

can u point us to line 124??

I've encountered a similar error message before when i using HP-UX on 
Intel Itanium.
The compiler complained that i used a non-constant in a static array 
declaration...
char a[ maxLen ] ;

in the end, I had to malloc/calloc them... (since i didnt know how to 
tweak or instruct
the compiler to ignore such errors... since the code was already old and 
compilable on
other hp-ux platforms)

-Ron

>
> Scott wrote:
>
>> Hi,
>>
>> It has been a LONG TIME since I've done any programming in C. I have
>> two old programs still in use which were developed on msdos, using the
>> "Mark Williams Let's C" compiler. We're talking 1980's stuff here.
>>
>> Anyway, I thought to try to port them to linux. Can anyone tell me
>> what I'm doing wrong?
>>
>> Here are the relevant portions of indatax.c:
>>
>> char *namectrl = NULL;
>> char *name1 = NULL;
>> char *name2 = NULL;
>>
>> typedef struct {
>>     char *var;    /* destination for storage of the data */
>>     size_t len;    /* max len of the data */
>>     char *(*xlat)();    /* translation routine */
>> } DATUM;
>>
>> DATUM recip_data[] = {
>> {  namectrl, NAMECTRL_LEN, make_upper },
>> {  name1, NAME1_LEN, make_upper },
>> {  name2, NAME2_LEN, make_upper },
>> [...]
>>
>> And these are the errors...
>>
>> indatax.c:124: initializer element is not constant
>> indatax.c:124: (near initialization for `recip_data[0].var')
>> indatax.c:125: initializer element is not constant
>> indatax.c:125: (near initialization for `recip_data[1].var')
>> indatax.c:126: initializer element is not constant
>> indatax.c:126: (near initialization for `recip_data[2].var')
>> [...]
>>
>> gcc version 2.95.3
>>
>> Thanks,
>>
>> Scott Swanson
>> Pendroy, Montana
>> -
>> To unsubscribe from this list: send the line "unsubscribe 
>> linux-c-programming" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>>
>>  
>>
>
>

Re: Initializer element is not constant

[Scott]

On Fri, Jan 21, 2005 at 10:37:12AM +0800, Ron Michael Khu wrote:
> Hi,
> 
> can u point us to line 124??
> 
> >>DATUM recip_data[] = {
> >>{  namectrl, NAMECTRL_LEN, make_upper },        <-- Line 124
> >>{  name1, NAME1_LEN, make_upper },

Re: Initializer element is not constant

[Ron Michael Khu]

have u tried changing the first field of each element??
something like... replacing those char ptrs with something static?

example:

DATUM recip_data[] = {
{  "i am a constant str", NAMECTRL_LEN, make_upper },       
{  "i am a constant str", NAME1_LEN, make_upper },

u might notice that some of  "initializer element is not constant" 
errors will be significantly reduced....

perhaps, the compiler is complaining that u have used something 
"dynamic"(or at least non-static) in defining a
"statically" allocated data structure(recip_data)
=(

perhaps u can change the way u define/declare ur variables/data 
structures....


Scott wrote:

>On Fri, Jan 21, 2005 at 10:37:12AM +0800, Ron Michael Khu wrote:
>  
>
>>Hi,
>>
>>can u point us to line 124??
>>
>>    
>>
>>>>DATUM recip_data[] = {
>>>>{  namectrl, NAMECTRL_LEN, make_upper },        <-- Line 124
>>>>{  name1, NAME1_LEN, make_upper },
>>>>        
>>>>
>-
>To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>  
>

Re: Initializer element is not constant

[Scott]

On Sat, Jan 22, 2005 at 01:46:31AM +0800, Ron Michael Khu wrote:
> have u tried changing the first field of each element??
> something like... replacing those char ptrs with something static?
> 
> example:
> 
> DATUM recip_data[] = {
> {  "i am a constant str", NAMECTRL_LEN, make_upper },       
> {  "i am a constant str", NAME1_LEN, make_upper },

As I recalled, the ability to HAVE dynamic pointers was one of the
primary benefits of using c in the first place! Later in the file I
have this routine which allocates space for each pointer in the
structure:

alloc_space(r) RECORD *r;
{	register size_t i;
	register char **v;
	
	for(i=0; i<r->n; i++)
	{	if(r->data[i].len == 0 || r->data[i].len == 0xFFFF) continue;
		v = (r->data[i].var);
		if (*v == NULL)
		{	*v = (char *) calloc(1,r->data[i].len + 1);
			memset(*v,'A'+i,r->data[i].len);
		}
	}
}

I guess i just don't understand why a "modern" compiler wants to
restrict my options in this fashion....

Re: Initializer element is not constant

[Ron Michael Khu]

but u can.... =)
have u tried dynamically allocating space for recip_data?? instead of 
the usual static declaration?
char a[10] <-- this is static
char a[]= {'1','2','3','4'} <-- this is static with definition and 
declartion in one
char *a = calloc.....

have u tried it? using malloc/calloc for defining DATUM recip_data??

im not good with explanations....
but i bet the gurus like JBG could explain the solution/scenario alot 
better. =)


Scott wrote:

>On Sat, Jan 22, 2005 at 01:46:31AM +0800, Ron Michael Khu wrote:
>  
>
>>have u tried changing the first field of each element??
>>something like... replacing those char ptrs with something static?
>>
>>example:
>>
>>DATUM recip_data[] = {
>>{  "i am a constant str", NAMECTRL_LEN, make_upper },       
>>{  "i am a constant str", NAME1_LEN, make_upper },
>>    
>>
>
>As I recalled, the ability to HAVE dynamic pointers was one of the
>primary benefits of using c in the first place! Later in the file I
>have this routine which allocates space for each pointer in the
>structure:
>
>alloc_space(r) RECORD *r;
>{	register size_t i;
>	register char **v;
>	
>	for(i=0; i<r->n; i++)
>	{	if(r->data[i].len == 0 || r->data[i].len == 0xFFFF) continue;
>		v = (r->data[i].var);
>		if (*v == NULL)
>		{	*v = (char *) calloc(1,r->data[i].len + 1);
>			memset(*v,'A'+i,r->data[i].len);
>		}
>	}
>}
>
>I guess i just don't understand why a "modern" compiler wants to
>restrict my options in this fashion....
>-
>To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>  
>

Re: Initializer element is not constant

[Scott]

On Sat, Jan 22, 2005 at 03:50:02AM +0800, Ron Michael Khu wrote:
> but u can.... =)
> have u tried dynamically allocating space for recip_data?? instead of 
> the usual static declaration?
> char a[10] <-- this is static
> char a[]= {'1','2','3','4'} <-- this is static with definition and 
> declartion in one
> char *a = calloc.....
> 
> have u tried it? using malloc/calloc for defining DATUM recip_data??

Well yes, I guess I could [m|c]alloc the recip_data array. But how do I
then populate it?

 recip_data[0].var = namectrl;
 recip_data[0].len = NAMECTRL_LEN;
 recip_data[0].xlat = make_upper;
etc...

How tedious is THAT!? Especially considering that the code has
eight such arrays, averaging 6 elements per array.

Maybe I'm not understanding your suggestion. As I mentioned, it has
been quite a while since I did any c programming. I just find it
strange that code which compiled fine 20 years ago now will not. I
could understand if it just generated warnings....

Re: Initializer element is not constant

[Christoph Bussenius]

Hi Scott,

On Fri, Jan 21, 2005 at 02:31:57PM -0700, Scott wrote:
>  recip_data[0].var = namectrl;

namectrl is NULL, so why would you want to do this?  This is just like
writing

recip_data[0] = NULL;

I am not quite sure what you intend to do, but I guess that you want
namectrl to change when you change recip_data[0].  To accomplish this,
you could make recip_data[0] a pointer to a pointer:

char *namectrl = NULL;
char *name1 = NULL;
char *name2 = NULL;

typedef struct {
        char **var;      /* destination for storage of the data */
        size_t len;     /* max len of the data */
        char *(*xlat)();        /* translation routine */
} DATUM;                                                                                        

DATUM recip_data[] = {
{  &namectrl, NAMECTRL_LEN, make_upper },
{  &name1, NAME1_LEN, make_upper },
{  &name2, NAME2_LEN, make_upper },
[...]

Now you can change namectrl by saying
*recip_data[0].var = "test string";

Hope this helps,
Christoph

-- 
``There's no dark side of the moon, really
Matter of fact, it's all dark''

--Pink Floyd

Re: Initializer element is not constant

[Scott]

On Sat, Jan 22, 2005 at 10:12:06PM +0100, Christoph Bussenius wrote:
> I am not quite sure what you intend to do, but I guess that you want
> namectrl to change when you change recip_data[0].  To accomplish this,
> you could make recip_data[0] a pointer to a pointer:
> 
> char *namectrl = NULL;
> char *name1 = NULL;
> char *name2 = NULL;
> 
> typedef struct {
>         char **var;      /* destination for storage of the data */
>         size_t len;     /* max len of the data */
>         char *(*xlat)();        /* translation routine */
> } DATUM;                                                                                        
> 
> DATUM recip_data[] = {
> {  &namectrl, NAMECTRL_LEN, make_upper },
> {  &name1, NAME1_LEN, make_upper },
> {  &name2, NAME2_LEN, make_upper },
> [...]
> 

Right! As I said, my c is quite rusty. Now as I recall, there was some
problem with the old dos compiler which prevented this syntax but
allowed the erroneous one. That, or I didn't understand what I was
doing and the compiler let me get away with it.... Looking at the code
in more detail, I see that it relies upon some bcd math module I'd written
in assembler, so the odds of this getting ported are pretty
slim. Thanks for the help, though!

Scott Swanson

RE: Initializer element is not constant

[Huber, George K RDECOM CERDEC STCD SRI]

Scott wrote:

>Here are the relevant portions of indatax.c:

>char *namectrl = NULL;
>char *name1 = NULL;
>char *name2 = NULL;

>typedef struct {
>	char *var;	/* destination for storage of the data */
>	size_t len;	/* max len of the data */
>	char *(*xlat)();	/* translation routine */
>} DATUM;

>DATUM recip_data[] = {
>{  namectrl, NAMECTRL_LEN, make_upper },
>{  name1, NAME1_LEN, make_upper },
>{  name2, NAME2_LEN, make_upper },
>[...]

>And these are the errors...

>indatax.c:124: initializer element is not constant
>indatax.c:124: (near initialization for `recip_data[0].var')
>indatax.c:125: initializer element is not constant
>indatax.c:125: (near initialization for `recip_data[1].var')
>indatax.c:126: initializer element is not constant
>indatax.c:126: (near initialization for `recip_data[2].var')
>[...]

First, I would upgrade to a more modern version of gcc.  The 
current release is the 3.4 series.   

Secondly, I tried the following program,

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include <stdio.h>
#include <stdlib.h>

#define NAMECTL_LEN   15
#define NAME_LEN       10

typedef struct tag_datum
{
    char*   var;
    size_t  len;
    char    *(*xlat)();
} datum;

char* make_upper()
{
    return NULL;
}

int main(int argc, char** argv)
{
    char*    namectrl = NULL;
    char*    name1 = NULL;
    char*    name2 = NULL;

    datum    data[] = {{namectrl, NAMECTL_LEN, make_upper},
                       {name1, NAME_LEN, make_upper},
                       {name2, NAME_LEN, make_upper}};

    return 0;
}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

When I compiled this program using gcc 3.4.2 with the flags `-ansi
-pedantic -Wall' I get a number of warnings stating:
"Initializer element is not computable at load time" 
Two per each line of initializing data.  My guess is that the compiler
can-not figure out how to initialize the first element of the structure
at run time because namectrl has yet to "created".  


However, all is not lost, changing the program to:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#include <stdio.h>
#include <stdlib.h>

#define NAMECTL_LEN   15
#define NAME_LEN       10

typedef struct tag_datum
{
    char*   var;
    size_t  len;
    char    *(*xlat)();
} datum;

char* make_upper()
{
    return NULL;
}

int main(int argc, char** argv)
{
    datum    data[] = {{NULL, NAMECTL_LEN, make_upper},
                       {NULL, NAME_LEN, make_upper},
                       {NULL, NAME_LEN, make_upper}};

    return 0;
}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

results in a clean compilation (except for a warning about
an unused variable).  To initialize the var member of datum, you
should be able to do something like:

  if(NULL != (data[0].var = malloc(NAMECTL_LEN*sizeof(char))))
  {
      strncpy(data[0].var, "test string", NAMECTL_LEN);
  }

and you should be able to use datum like this:

  int   i, num = sizeof(data)/sizeof(datum);
  for(i = 0; i < num; i++)
  {
      printf("data point %d, var %s\n", i, (data[i].var ? data[i].var : "N/A"));
  }

hope this helps,
George

Re: Initializer element is not constant

[Scott]

On Mon, Jan 24, 2005 at 04:09:30PM -0500, Huber, George K RDECOM CERDEC STCD SRI wrote:
> 
> First, I would upgrade to a more modern version of gcc.  The 
> current release is the 3.4 series.   

Yeah, everything I have on this machine is pretty ancient....

> 
> Secondly, I tried the following program,

   [big snip...]
> 
> hope this helps,
> George

Yes, it certainly does! Thanks so much to you and the others on the
list. I'm sort of excited thinking about coming back to C after a long
sojourn with perl. Can you recommend a good on-line tutorial to
refresh my failing memory?

Scott Swanson