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From: bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: C23 thoughts and opinions
Date: Sat, 1 Jun 2024 19:59:19 +0100
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On 01/06/2024 11:24, bart wrote:
> On 01/06/2024 02:25, Scott Lurndal wrote:

[objcopy]

> 
> Nope, same thing. This doesn't inspire much confidence. With values 
> shown, the actual size IS contained within the _size value, but only as 
> the last 16 bits of the value.
> 
> gcc versions were 10.3.0 and 9.4.0 respectively; the latter is what is 
> provided by Windows 11.
> 
> You also brought up the fact that the size is not known to the compiler 
> anyway, which means a few things are not possible, like using the size 
> in a static context.

I thought I'd dash off my own version of 'objcopy' to see if I could do 
any better. This version does binary/text to COFF only. The input file 
here was a .wav file:

   C:\qapps>qq objcopy test.wav   # running my objcopy
   Compiling test.m to test.obj
   Written test.obj               # haven't settled on naming schemes yet
   char[] name is: test_wav
   u64 size name is: test_wav_len

   C:\qapps>gcc demo.c test.obj

   C:\qapps>a
   Size = 14355
   Data = 52 49 46 ...

The demo.c file is this:

   #include <stdio.h>

   extern char test_wav[];
   extern long long test_wav_len;

   int main(void) {
       printf("Size = %lld\n", test_wav_len);
       printf("Data = %02x %02x %02x ...\n", test_wav[0], test_wav[1], 
test_wav[2]);
   }


And this is info about the binary to show the right data has got into 
the C program:

   C:\qapps>dir test.wav
   01/11/1996  04:05            14,354 test.wav

   C:\qapps>dump test.wav
   Dump of test.wav; Size = 14354 bytes
   0000: 52 49 46 46 0A 38 00 00 57 41 56 45 66 6D 74 20    RIFF.8..WAVEfmt

There is one slight discrepancy: the size from the C file is one byte 
bigger; that's because I'm using 'strinclude' (in the code compiled 
during the process, which adds a terminator. I can fix that easily, or 
allow the option.

The script used to implement my 'objcopy' is shown below. It writes out 
a 2-line program which is compiled by my systems language into an object 
file.



------------------------------------------------

     proc main=
         if ncmdparams<1 then
             println "Usage:"
             println "  qq objcopy filename [name]"
             stop
         fi

         infile:=cmdparams[1]
         basename:=extractbasefile(infile)
         mfile:=basename+".m"
         objfile:=basename+".obj"
         if infile in (mfile, objfile) then abort("Name clash") fi

         name:=basename+"_"+extractext(infile)
         if ncmdparams>1 then
             name:=cmdparams[2]
         fi

         writetextfile(mfile, (
                 sfprint("export []byte # = strinclude(""#"")",name, 
infile),
                 sfprint("export int #_len = #.len", name, name)
             )
         )

         if system("mm -obj "+mfile)<>0 then
             abort("Compile error on "+mfile)
         else
             println "Written", objfile
             println "char[] name is:",name
             println "u64 size name is:",name+"_len"
         fi
     end