Path: csiph.com!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Suggested method for returning a string from a C program?
Date: Tue, 18 Mar 2025 19:05:11 -0700
Organization: None to speak of
Lines: 64
Message-ID: <87plidvkq0.fsf@nosuchdomain.example.com>
References: <vrd77d$3nvtf$2@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Date: Wed, 19 Mar 2025 03:05:13 +0100 (CET)
Injection-Info: dont-email.me; posting-host="6b2adc3539d30183fea78a893643ef1f"; logging-data="3935211"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+tj6M1IS8ExPAUCjh9DynV"
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:UfnTzVXc6bOy/TEUyX2e/tZ9+KY= sha1:A9CByKALBQCCBfNEOwv2fgfOlUM=
Xref: csiph.com comp.lang.c:391320

DFS <nospam@dfs.com> writes:
> I'm doing these algorithm problems at
> https://cses.fi/problemset/list/
>
> For instance: Weird Algorithm
> https://cses.fi/problemset/task/1068
>
> My code works fine locally (prints the correct solution to the
> console), but when I submit the .c file the auto-tester flags it with
> 'runtime error' and says the output is empty.
>
> ------------------------------------------------------------
> // If n is even, divide it by two.
> // If n is odd, multiply it by three and add one.
> // Repeat until n is one.
> // n = 3: output is 3 10 5 16 8 4 2 1
>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
>
> int main(int argc, char *argv[])
> {
>     int n = atoi(argv[1]);
>     int len = 0;
>     char result[10000] = "";
>     sprintf(result, "%d ", n);
>
>     while(1) {
>         if((n % 2) == 0)
>             {n /= 2;}
>         else
>             {n = (n * 3) + 1;}
>
>         if(n != 1)
>             {
>                 len = strlen(result);
>                 sprintf(result + len, "%d ", n);
>             }
>         else
>             break;
>     }
>
>     len = strlen(result);
>     sprintf(result + len, "1 ");
>     printf("%s\n",result);
>
>     return 0;
> }
> ------------------------------------------------------------

I don't see any problem with the code, and neither does gcc on
my system.  But the code you posted contains a number of NO-BREAK
SPACE characters (0xa0).  "clang -Wno-unicode-whitespace" accepts
those characters without complaint, and gives non-fatal warnings
without that option.  gcc treats them as a fatal error.

A minor point: You print a trailing space.  I don't know whether
the auto-tester will accept that.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */