snprintf() doesn't use format size specifiers

Norman Feske norman.feske at ...1...
Tue Apr 21 10:08:39 CEST 2015

Hello Pirmin,

> If I try to format some data in a anligned string with  
> Genode::snprintf(), the data is stored in the string, but my  
> additional format specifier for the field width aren't respected.
> My string is:
> static const char* lineFormat = "%5d  \"%25s\"  \"%25s\" %10s %5d\r\n"

Genode's format-string functions are limited to the few use cases
present in the base framework. I.e., it is sufficient for simple tasks
like printing a number or concatenating strings but it is not meant as a
full-fledged POSIX compliant formatting utility. If you need a complete
format-string implementation, I recommend you to use the libc instead.

> If I do want to right align the numbers (%-5d) the function crashes my  
> program.

This should not happen. Thank you for reporting. I just opened an issue
about it:

> The comment on the functoin doesn't specify that format sizes arn't supported.

I keep a note to cover this information in the upcoming documentation.
For now, please let me refer you to the implementation. I think the code
is pretty self-explanatory. If not, please don't hesitate to ask.

Best regards

Dr.-Ing. Norman Feske
Genode Labs ·

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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