Mailinglist Archive: opensuse (2532 mails)

[Sam Clemens <clemens.sam1@xxxxxxxxx>]

David C. Rankin wrote:
> Listmates,
>
>     I was comparing input handling between perl and c and I ran into a 
> very weird problem with the strtof function in c. What am I doing wrong? 
> strtof doesn't seem to be working like the man page shows. Here is my 
> test bit of code:
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <string.h>
>
> int main(int argc, char *argv[])
> {
>     char *endptr, *str, newstr[20];
>     float val, newval;
>
>     if (argc < 2) {
>         fprintf(stderr, "Usage: %s number\n", argv[0]);
>     exit(1);
>     }
>
>     str = argv[1];
>     printf("\nstr = %s\nsizeof str = %d\nstrlen str = %d\n", str, 
> sizeof(str), strlen(str));
>     
>     strcpy(newstr,argv[1]);
>     printf("\nnewstr = %s\nsizeof str = %d\nstrlen str = %d\n\n", 
> newstr, sizeof(newstr), strlen(newstr));
>     
>     val = strtof(str, &endptr);

endptr is uninitialized,
so it's pointing at some random memory location.

>     newval = strtof(newstr, &endptr);
>     
>     if (*endptr != '\0')
>         printf("Additional characters after number: %s\n", endptr);
>
>     printf("str:\tstrtof of %s = %f\n", str, val);
>     printf("newstr:\tstrtof of %s = %f\n\n", newstr, newval);
>
>
>     return(0);
> }
>
>     The code compiles without error or warning with: "gcc -o prg/tmp 
> src/tmp.c" Here is the bewildering output:
>
> 20:03 Rankin-P35a~/linux/programming/c> ./prg/tmp 250.871
>
> str = 250.871
> sizeof str = 4
> strlen str = 7
>
> newstr = 250.871
> sizeof str = 20
> strlen str = 7
>
> str:    strtof of 250.871 = 1132125952.000000
> newstr: strtof of 250.871 = 1132125952.000000
>
>     Obviously I must be missing something very simple, but I can't put 
> my hands on it. Help?

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