test, bench, precompute_ecmult: use EXIT_... constants for main return values

src/precompute_ecmult_gen.c

@@ -6,6 +6,7 @@
 
 #include <inttypes.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 #include "../include/secp256k1.h"
 
@@ -64,7 +65,7 @@ int main(int argc, char **argv) {
     fp = fopen(outfile, "w");
     if (fp == NULL) {
         fprintf(stderr, "Could not open %s for writing!\n", outfile);
-        return -1;
+        return EXIT_FAILURE;
     }
 
     fprintf(fp, "/* This file was automatically generated by precompute_ecmult_gen. */\n");
@@ -96,5 +97,5 @@ int main(int argc, char **argv) {
     fprintf(fp, "#undef S\n");
     fclose(fp);
 
-    return 0;
+    return EXIT_SUCCESS;
 }