Re: C23 thoughts and opinions

On 30/05/2024 15:08, Michael S wrote:

On Thu, 30 May 2024 14:34:00 +0100
bart <bc@freeuk.com> wrote:
 

On 30/05/2024 03:32, Lawrence D'Oliveiro wrote:

On Wed, 29 May 2024 13:58:20 +0200, Bonita Montero wrote:
  

I've got a small commandline-tool that makes a const'd char
-array from any binary file.

>
It seems to me it would be more efficient to use objcopy to turn
that binary file directly into an object file with symbols
accessible from C code defining its beginning and ending points.
Then just link it into the executable.

>
None of my compilers, whether for C or anything else, generate object
files.
>
However, suppose I wanted to link a file called 'logo.bmp' say, into
my program, which consisted of a file called main.c.
>
What is the entire process using your suggestion? What do I put into
main.c? Assume the data is represented by a char-array.
>

 extern unsigned char _binary_logo_bmp_start[];
extern unsigned char _binary_logo_bmp_size[];
 The first symbol is an array itself.
The seconded symbol contains the length of array. You use it in somewhat
non-intuitive way:
   size_t my_size = (size_t)_binary_logo_bmp_size;
 Pay attention that I never used this method myself, just took a look at
the output of objcopy with 'objdump -t', so please don't take my words
as a sure thing.
 BTW, options in this case are rather simple:
objcopy -I binary -O elf32-little logo.bmp logo_bmp.o

Where do the _binary_logo_bmp_start and ...-size symbols come from? That is, how do they get into the object file.

Replace elf32-little with relevant format for your software. However I
am not sure that it would work for none-elf output formats.

There appears to be an objcopy utility that runs under Windows.