[OpenWrt-Devel] stdout and putchar() behavior in musl

Arjen de Korte arjen+openwrt at de-korte.org
Wed Mar 30 07:27:57 EDT 2016

Citeren Ram Chandra Jangir <rjangi at codeaurora.org>:

> Hi,
> Did anyone observed stdout and putchar() behavior differences between musl &
> uClibc?
> I have below code snippet :
> int main(void){
> 	int c;
> 	while((c=getchar())!= 'e')     {
> 		putchar(c+1);
> 	}
> 	return 0;
> }
> When I use uClibc/gcc, I can see writing c+1 from putchar() happening
> immediately. But when I use musl, character(c+1) gets printed on console
> only if I exit from the program by entering 'e'.
> I guess printing character using putchar family on stdio is having bug(or
> different implementation) in musl. Has anybody faced this issue? Any
> workaround?

Apparently in uClibc stdout is unbuffered and in musl it is buffered.  
Either is allowed in the C-standard (it is  not specified) so this is  
not a bug. If you want each character to be output immediately, you  
probably need to add flush(stdout).
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