Re: [musl] printf does not print anything (musl 1.2.3)

[Gabriel Ravier <gabravier@gmail.com>]

On 4/12/23 23:35, Detlef Riekenberg wrote:
> The attached test fails with musl 1.2.3 (does not print anything):
>
>
> os: xubuntu 23.04
> compiled with:  musl-gcc  -O0  -std=c99  -Wall  prog.c  -o  prog_musl-O0
> gcc: 12.2.0-17ubuntu1
>
>
> The programm is a tic-tac-toe game, but the source is stange:
> * Filesize Original: 2745 byte (includes only <stdio.h>)
> * Filesize after preprocess: with musl ~559k / with gnu libc ~571k
> * After preprocess, the format string is ~100kb
> * main() uses only one printf, and one arg has a scanf:
>
> `
> int main() {
>      while(*d) printf(fmt, arg);
> }
> `
>
> For testing, i removed the "while(*d)",
> but the binary using musl still does not print anything.
>
>
> Compiling the original source with the same gcc and using gnu libc works
> and the gnu libc version with the removed "while (*d)" produces an output of 23592 byte.
>
>
> ioccc page:  https://www.ioccc.org/2020/carlini/index.html
> Also available on github:  https://github.com/carlini/printf-tac-toe
>
>
> I tried to subscribe to the list, but i have no confirmation yet, so please cc me.
>
>
> --
> Bye bye ... Detlef

The printf call in the linked program attempts to use printf with 
numbered argument conversion specifications with a position larger than 
9 (such as 42). This is not portable to all POSIX systems, as POSIX 
specifies that the implementation need only support numbered argument 
conversion specifications with a position that is at most as large as 
the NL_ARGMAX macro (defined in limits.h), and POSIX's minimum 
requirement on the value of NL_ARGMAX is only of 9.


Thusly, musl defines NL_ARGMAX to 9 and errors on numbered argument 
conversion specifications with a position larger than it.