atof coredump with getopt - c++

Question

I'm writing a C++ application which converts fahrenheit to celsius and kelvin, and kelvin to celsius and fahrenheit, etc. Since it's stupid to write an interative application here, I decided to familiarize myself with the getopt function in unistd.h.
Format:
F2C -k 273.15
Output:
FAHR CELSIUS KELVIN
32 0 273.15
Here is my code:
#include <iostream>
#include <stdlib.h>
#include <unistd.h>
#define VERSION 0.1
#define HELP help(argv[0])
#define OPTS "vk:f:c:h"
float ver = (float)VERSION;
void help(char *s);
namespace Fahrenheit
{
float FK(float F) {
return ((5.0/9.0) * (F - 32.0) + 273.15);
}
float FC(float F) {
return ((5.0/9.0) * (F - 32.0));
}
void printfahr(float F) {
std::cout << "FAHR\t\tCELSIUS\t\tKELVIN" << std::endl;
std::cout << F << "\t\t" << FC(F) << "\t\t" << FK(F) << std::endl;
}
}
namespace Celsius
{
float CF(float C) {
return ((C*(9/5)) + 32);
}
float CK(float C) {
return (C+273.15);
}
void printc(float C) {
std::cout << "FAHR\t\tCELSIUS\t\tKELVIN" << std::endl;
std::cout << CF(C) << "\t\t" << C << "\t\t" << CK(C) << std::endl;
}
}
namespace Kelvin
{
float KF(float K) {
return (((9.0/5.0) * (K-273.15)) + 32);
}
float KC(float K) {
return (K-273.15);
}
void printk(float K) {
std::cout << "FAHR\t\tCELSIUS\t\tKELVIN" << std::endl;
std::cout << KF(K) << "\t\t" << KC(K) << "\t\t" << K << std::endl;
}
}
int main(int argc, char *argv[])
{
char arg = '\0';
if(argc < 2 && argc == 1 && argc > 0) {
help(argv[0]);
exit(1);
}
/*** Use function getopt() defined in unistd.h to accept 5 arguments: -v, -h, -k, -f, and -c ***/
while((arg=getopt(argc, argv, OPTS))!=-1)
{
float floatarg = atof(optarg);
switch(arg)
{
case 'v':
std::cout << "The current version is:" << ver << std::endl;
break;
case 'h':
HELP;
break;
case 'k':
Kelvin::printk(floatarg);
break;
case 'f':
Fahrenheit::printfahr(floatarg);
break;
case 'c':
Celsius::printc(floatarg);
break;
default:
HELP;
break;
}
}
return 0;
}
void help(char *s) {
std::cout << "Usage:\t"<< s << " [-option] [argument]" << std::endl;
std::cout << "option:\t" << "-c [temperature]: convert a Celsius temperature to Fahrenheit and Kelvin" << std::endl;
std::cout << "\t" << "-f [temperature]: convert a Fahrenheit temperature to Celsius and Kelvin" << std::endl;
std::cout << "\t" << "-h: show help information" << std::endl;
std::cout << "\t" << "-k [temperature]: convert a Kelvin temperature to Fahrenheit and Celsius" << std::endl;
std::cout << "\t" << "-v: show version information" << std::endl;
}
My problem is that whenever I use an option that accepts no arguments (like -v) I get a core dump.
dbx has shown me that the SIGSEV occurs at line 70 (float floatarg = atof(optarg);).
When I run the program like this:
./F2C -k 273.15
The math is done correctly and I get a clear printout. It's only when I use -v or -h that my program SIGSEV's.
Extra information:
This program was compiled with the Sun studio compiler suite, version 5.12.
I'm completely baffled as to why my program SIGSEV's. It is inconsistent and makes no sense.
I would appreciate any help available.

Answer 1

Should have done some optarg checking. After all, you can't convert null to a float.
new main():
#define FLOATARG atof(optarg)
int main(int argc, char *argv[])
{
char arg = '\0';
if(argc < 2 && argc == 1 && argc > 0) {
help(argv[0]);
exit(1);
}
/*** Use function getopt() defined in unistd.h to accept 5 arguments: -v, -h, -k, -f, and -c ***/
while((arg=getopt(argc, argv, OPTS))!=-1)
{
switch(arg)
{
case 'v':
std::cout << "The current version is: << ver << std::endl;
break;
case 'h':
HELP;
break;
case 'k':
Kelvin::printk(FLOATARG);
break;
case 'f':
Fahrenheit::printfahr(FLOATARG);
break;
case 'c':
Celsius::printc(FLOATARG);
break;
default:
HELP;
break;
}
}
return 0;
}

Answer 2

The shortest fix is:
float floatarg = optarg ? atof(optarg) : 0.0;
You can also rewrite your code like
float floatarg = 0.0;
switch(arg)
{
case 'v':
std::cout << "The current version is:" << ver << std::endl;
break;
case 'h':
HELP;
break;
case 'k':
floatarg = atof(optarg);
Kelvin::printk(floatarg);
break;
case 'f':
floatarg = atof(optarg);
Fahrenheit::printfahr(floatarg);
break;
...
or
float floatarg = 0.0;
if(optarg) {
floatarg = atof(optarg);
}
switch(arg)
{
case 'v':
std::cout << "The current version is:" << ver << std::endl;
break;
case 'h':
HELP;
break;
case 'k':
Kelvin::printk(floatarg);
break;
case 'f':
Fahrenheit::printfahr(floatarg);
break;
...