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Please help. GNU As syntax for pointers with ANSI C binding in platform independent way.

Oleksandr Gavenko gavenko@bifit.com.ua
Wed Nov 10 17:25:00 GMT 2010 
I want include binary data in executable.

For this purpose I use such techniques (from my Makefile):

%.o %.h: %.bin
	echo "extern const char *$*;" >$*.h
	echo '.text; .global $*; $*_data:; .incbin "$*.bin"; $*:; .int 
$*_data;' | gcc -x assembler -o $*.o -c -

This cryptic code equivalents to .S file (when 'str.bin' processed):

     .text
     .global str
str_data:
     .incbin "str.bin"
str:
     .int str_data      # XXX .int or .quad ???

To access the data from str.bin I use in .c:

================================================================
#include "str.h"  /* here placed: extern const char *str; */

int foo() {
     printf(str);
}
================================================================

In case of 32-bit platform I need wrote '.int', in case of
64-bit platform I need wrote '.quad' in assembler.

To work around I can use #if/#define and preprocess output.

But this seems ugly. Is there portable syntax?


Also I don't understand way I can not directly point str_data in
printf() call. Why I need wrote '&' before 'str_data' in .c:

================================================================
extern const char str_data;  /* For type resolving I don't declare 
pointer */
int foo() {
     printf(&str_data);  /* because C compiler think that str_data is 
data itself, do not point to it! */
}
================================================================

to satisfy ANSI C types and make executable correct working?


To get ability use natural C style code I use another symbol
'str' that point to actual data in 'str_data':

================================================================
str:
     .int str_data  # XXX .int or .quad ???
================================================================

so in .c file can place:

================================================================
extern const char *str;  /* Real pointer. */
...
    printf(str);    /* No ugly dereferencing. */
================================================================

So questions:

   1) is correctly I declare pointer to data from .S for C sources or
      there are exist another true way?
   2) can I make pointer in .S in portable way (to avoid use of .int/.quad)?
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