Re: [Patch] argp: fix line wrapping in --help output

[Simon Reinhardt]

ping

Am 09.02.2016 um 16:51 schrieb Simon Reinhardt:
> Hi,
> 
> Argp provides line wrapping of help and usage output. For this it
> maintains a buffer in the struct argp_fmtstream_t. During line breaking
> the buffer's contents grow due to the inserted spaces needed to indent
> the lines (function __argp_fmtstream_update in lib/argp-fmtstream.c).
> This breaks once the buffer is full and produces malformatted output.
> Example program:
> 
> #include <config.h>
> #include <argp.h>
> 
> static struct argp_option options[] = {
>   {"test", 't', 0, 0, "1\n2\n3\n4\n5\n6"},
>   {0}
> };
> 
> static struct argp argp = {options};
> 
> int
> main (int argc, char **argv)
> {
>   argp_parse(&argp, argc, argv, 0, 0, 0);
>   return 0;
> }
> 
> This gives
> $ ./report --help
>                              Usage: report [OPTION...]
> 
>   -t, --test                 1
>                              2
>                              3
>                              4
>                              5
> 6
>   -?, --help                 give this help list
>       --usage                give a short usage message
> 
> The indentation that should prefix the '6' erroneously prefixes the
> 'Usage' line.
> 
> The suggested fix to __argp_fmtstream_update works by making it flush
> everything ASAP. This way no formatting of content inside the buffer is
> needed.
> 
> This passes the existing tests (test-argp.c, test-argp-2.sh). In
> addition it produces identical --help and --usage output for GNU tar's
> large option table (see attached file tar.c).
> 
> Further Nitpicking:
> 
> before overlong words that exceed the line length one gets a spurious
> newline before the word:
> 
> static struct argp_option options[] = {
>   {"x", 'x', 0, 0,
> "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
>    "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"},
>   {0}
> };
> 
> will produce the --help output
> Usage: bigword [OPTION...]
> 
>   -x, --x
>                              xxxxxxx(...)
>   -?, --help                 give this help list
>       --usage                give a short usage message
> 
> This is fixed by flushing at the end of indent_to in argp-help.c
> 
> Cheers,
> Simon
>