best way to create a string array through macro - c

Question

I am trying to crate a parametric static array in a header file.
Let me elaborate my requirement
Wanted to create below array in header file statically which can be resolved at
compile time
static char test_array[][256] = {
"hello_1",
"hello_2",
"hello_3" };
I need to generate this using macro which can do substitution with %d for 1,2 and 3 and the number
of parameter also not fixed. What I mean here is tomorrow this array I can simply change through header file to
static char test_array[][256] = {
"hello_1",
"hello_45",
"hello_39",
"hello_101" };
I have the code to do it at run time in .c file but specifically I want to do it in a header file through macros .

Answer 1

The best way would be to write generator, that generates header array in compile time. A short time ago I wrote program that may point you the right direction:
/*
* Copyright (c) 2018 Krzysztof "Palaiologos" Szewczyk
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#define PERLINE 30
#define BUFSIZE 1024
static const char hexrange[] = "0123456789ABCDEF";
char buf[BUFSIZE];
int lineidx,line,i,bytes;
int main(int argc, const char * argv[]) {
FILE * in, * out;
if (argc != 4) {
fprintf(stderr, "Usage: %s infile outfile symbol\n", argv[0]);
return 1;
}
in = fopen(argv[1], "rb");
out = fopen(argv[2], "wb");
if (!in || !out) {
fputs("Could not open one of input files.\n", stderr);
return 1;
}
fprintf(out, "/* Generated by HexExport (by Krzysztof Szewczyk a.k.a. Palaiologos) */\n\n");
fprintf(out, "static const unsigned char %s[] = {", argv[3]);
while ((bytes = fread(buf, 1, sizeof(buf), in)) > 0) {
for (i = 0; i < bytes; ++i) {
int byte = ((uint8_t *)buf) [i];
if (lineidx++ == 0) {
if (line++)
fputc(',', out);
fputs("\n\t", out);
} else
fputs(", ", out);
fputs("0x", out);
fputc(hexrange[byte >> 4], out);
fputc(hexrange[byte & 0xF], out);
if (lineidx >= PERLINE)
lineidx = 0;
}
}
fputs("\n};\n", out);
fclose(in);
fclose(out);
return 0;
}
What it does, simply, is to generate hex array from file. You can modify it to accomplish your task. Generating such array using macro is either impossible or very hard task. Source code taken from this place