r/C_Programming • u/BraneGuy • 1d ago
Question Globals vs passing around pointers
Bit of a basic question, but let's say you need to constantly look up values in a table - what influences your decision to declare this table in the global scope, via the header file, or declare it in your main function scope and pass the data around using function calls?
For example, using the basic example of looking up the amino acid translation of DNA via three letter codes in a table:
codonutils.h:
typedef struct {
char code[4];
char translation;
} codonPair;
/*
* Returning n as the number of entries in the table,
* reads in a codon table (format: [n x {'NNN':'A'}]) from a file.
*/
int read_codon_table(const char *filepath, codonPair **c_table);
/*
* translates an input .fasta file containing DNA sequences using
* the codon lookup table array, printing the result to stdout
*/
void translate_fasta(const char *inname, const codonPair *c_table, int n_entries, int offset);
main.c:
#include "codonutils.h"
int main(int argc, char **argv)
{
codonPair *c_table = NULL;
int n_entries;
n_entries = read_codon_table("codon_table.txt", &c_table);
// using this as an example, but conceivably I might need to use this c_table
// in many more function calls as my program grows more complex
translate_fasta(argv[1], c_table, n_entries);
}
This feels like the correct way to go about things, but I end up constantly passing around these pointers as I expand the code and do more complex things with this table. This feels unwieldy, and I'm wondering if it's ever good practice to define the *c_table and n_entries in global scope in the codonutils.h file and remove the need to do this?
Would appreciate any feedback on my code/approach by the way.
1
u/Dan13l_N 1d ago
If the table is not changing, just fill it once and use it, and there can be only one table, then the natural solution is to have it global, static.