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i don't understand how to compile this.
I've didnt put all of the functions that i've made in this library because all of them work properly, and it's the first time that i have to use math.h
Until now i've compiled like this without issues:
gcc -c -g f.c
gcc -c -g main.c
gcc -o main main.o f.o
I've tried to insert -lm but i don't get how and where it has to be putted.
//header
#include<math.h>
#define MAX 5
typedef enum {FALSE, TRUE} bool;
typedef enum {ERROR=-1, OK=1} status;
status parse_int(char s[], int *val);
//function
#include<stdio.h>
#include<math.h>
#include <stdlib.h>
#include"f.h"
status parse_int(char s[], int *val) {
int l, val_convertito = 0, val_momentaneo = 0;
for(l = 0; s[l] != '\0'; l++);
for(int i = 0; s[i] != '\0'; i++) {
if(s[i] >= '0' && s[i] <= '9') {
val_momentaneo = ((int) (s[i]-48)) * ((int)exp10((double)l--));
val_convertito += val_momentaneo;
*val = val_convertito;
} else return ERROR;
}
return OK;
}
//main
#include<stdio.h>
#include<math.h>
#include <stdlib.h>
#include"f.h"
int main() {
int val_con, *val, ls;
char s_int[ls];
printf("Inserisci la lunghezza della stringa: ");
scanf("%d", &ls);
printf("\n");
printf("Inserisci l'intero da convertire: \n");
scanf("%s", s_int);
val = &val_con;
status F8 = parse_int(s_int, val);
switch(F8) {
case OK: printf("Valore convertito %d\n", val_con);
break;
case ERROR: printf("E' presente un carattere non numerico.\n");
break;
}
}
1 Answer
From the exp10 manual page:
SYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <math.h>
Link with -lm.
CONFORMING TO
These functions are GNU extensions.
Since these aren't standard functions, you not only need to have #include <math.h>, but you must have the line #define _GNU_SOURCE before the #include <math.h> line.
You also need to add -lm on the link line, so you'd have
gcc -o main main.o f.o -lm
The -l options normally come after all the .o files.
The easiest way to do all this is to use make. It already knows how to compile and link C files, so you just need to tell it which files depend on which other files, and change some variables to add customizations like -g and -lm.
Create a file named Makefile with these contents:
CFLAGS += -g
LDLIBS += -lm
main: main.o f.o
main.o: main.c f.h
f.o: f.c f.h
And then just type make:
$ make
cc -g -c -o main.o main.c
cc -g -c -o f.o f.c
cc main.o f.o -lm -o main
