Simple C code compiles on Leopard and Tiger, doesn't run on Leopard

Question

Hello all,
I have a simple program I wrote that reads in information from a file, does some stuff to it, and then writes a new file. The program compiles correctly on Leopard, Tiger, and Fedora, but only runs correctly on Tiger and Fedora. The output file of the Leopard run program has a line of gibberish followed by missing information. I've compiled it on Leopard using both gcc versions 4.0.1 (the Leopard standard) and 4.2.2, and still get the same bad output file. Any thoughts?
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int main () {
int n=0;
float p[5261][3];
char *line;
line=malloc(sizeof(char)*100);
FILE *inputfile;
inputfile=fopen("initial.crd","r");
FILE *outputfile;
outputfile=fopen("new.initial.crd","w");
char a[4], b[4], c[4];
int atomid,molid;
float phi, theta, d;
float r=2;
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
while(n<5260){
line=fgets(line,100,inputfile);
/printf("%s",line);/
sscanf(line,"%d%d%s%s%f%f%f%s",&atomid,&molid,&a,&b,&p[n][0],&p[n][1],&p[n][2], &c);
/*printf("%d %d %s %s %f %f %f %s\n",atomid,molid,a,b,p[n][0],p[n][1],p[n][2],c);*/
d=sqrt(powf(p[n][0],2)powf(p[n][1],2)powf(p[n][2],2));
d+=r;
theta=atan(p[n][1]/p[n][0]);
phi=atan2(p[n][1],p[n][2]);
fprintf(outputfile,"%5d%5d %-4s %-4s%10.5f%10.5f%10.5f %s\n",atomid,molid,a,b,dsin(phi)*cos(theta),d*sin(phi)*sin(theta),dcos(phi),c);
n++;
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
line=fgets(line,100,inputfile);
fprintf(outputfile,"%s",line);
fclose(inputfile);
fclose(outputfile);
return 0;
}

Answer 1

robkal wrote:
Also, the code shown, as is, runs perfectly on Tiger and various versions of Fedora. The output file from these OS's is perfect. Do you know of a reason that Leopard would be different?
<sigh> Somehow I knew you were going to say that.
The reason Leopard is different is because it is acting correctly whereas the other are not. Linux doesn't surprise me, but I would have expected more about of Tiger. That's unfortunate.
I just tried your code on my Linux box (I'm not at my Mac now) and it seg faults. I changed the sizes of a, b, and c to 5 and it runs properly. It has nothing to do with Leopard or 64 vs 32 bit. In C, if you store a string with 4 characters, you had better make room for 5.