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Message-ID: <20221218095852.GA2551@voyager>
Date: Sun, 18 Dec 2022 10:58:52 +0100
From: Markus Wichmann <nullplan@....net>
To: musl@...ts.openwall.com
Subject: Re: Bug in atoll strtoll, the output of then differ
On Sun, Dec 18, 2022 at 10:32:10AM +0100, Domingo Alvarez Duarte wrote:
> Hello !
>
> Doing some work with emscripten with this project
> https://github.com/mingodad/CG-SQL-Lua-playground I was getting some errors
> with the usage of "atoll" and with this small program to compare the output
> of "musl" and "glibc" I found what seems to be a bug in "atoll" because with
> "musl" it gives a different output than "strtoll".
>
> =====
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(int argc, char *argv[])
> {
> const char *s = "9223372036854775808";
> long long ll = atoll(s);
> long long ll2 = strtoll (s, (char **) NULL, 10);
> int imax = 0x7fffffff;
> printf("%s : %lld : %lld : %d : %d\n", s, ll, ll2, imax, ll <= imax);
> return 0;
> }
>
> =====
>
> Output from "glibc":
>
> =====
>
> 9223372036854775808 : 9223372036854775807 : 9223372036854775807 : 2147483647
> : 0
>
> =====
>
> Output from "musl":
>
> =====
>
> 9223372036854775808 : -9223372036854775808 : 9223372036854775807 :
> 2147483647 : 1
>
> =====
>
> Cheers !
>
Well, your problem here is that ato* behavior on error is not defined.
The C standard explicitly excepts behavior on error from the requirement
that these functions return the same thing as their strto* counterparts,
and §7.24.1 (of C23) explicitly states that behavior in that case is
undefined.
This means that a test case is wrong; no result is defined. Actually, a
crash would be acceptable behavior. This also means that when I return
to work next year, I should really go through my code base and replace
all ato* calls with their strto* counterparts for that reason alone.
Ciao,
Markus
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