打印填充的字符串数组将打印垃圾

Question

I'm just getting into C with a previous knowledge of RPG coding. Like many before me, I'm confused about strings, arrays and pointers and how to work with them.

I'm working on a program which takes the name, equatorial radius and polar radius of the planets from a data file, and then calculates and outputs volume, surface area.

My main function has the following declarations:

double       equi_rad[iNumPlanets]; /* equitoral radii of planets */
double       pol_rad[iNumPlanets];  /* polar radii of planets */
char         *name[iNumPlanets];    /* array containing planet name */

( iNumPlanets has already been initialized as 8)

I then call the function load :

load("radii.dat", equi_rad, pol_rad, iNumPlanets, name);

Load reads through the file in a loop and populates arrays. I've verified that this is working correctly within the function, so there seems no point copying out this bit of code. This is the prototype:

int load(const char* filename, double *equitoral_radii, double *polar_radii, const int iNumPlanets, char *planet_name[]);

Back in my main function, the equi_rad and pol_rad arrays are populated correctly and can be worked with. However, when I try to printf the name array contents, it's just random nonsense.

Can anyone explain why I can successfully modify the double arrays in a function, but not the string arrays?

Answer 1

Back in my main function, the equi_rad and pol_rad arrays are populated correctly and can be worked with. However when I try to printf the name array contents, it's just random nonsense.

You need to show the code. Guess is you are not correctly populating planet_name array. You might need to use malloc (eg, planet_name[i] = malloc(LENGTH) ), and copy the string contents there. Then you should have no issues. eg

planet_name[i] = malloc(strlen(sourceStr)+1);
strcpy(planet_name[i], sourceStr);

Don't forget to free each of the pointers for which you allocated data.