Re: [PATCH 1/2] maint.mk: Split long argument lists

[Bruno Haible]

Hi,

> The workaround is to split argument list into chunks that operating
> system can process. "getconf ARG_MAX" is used to determine size of the
> chunk.

Two questions on this:

1) People say that 'getconf ARG_MAX' returns the appromixate number
   of bytes in a command line. [1]
   But you use it with 'xargs -n', which gives a limit on the number of
   arguments. Shouldn't the patch use 'xargs -s' instead?

2) The really available values are slightly smaller.

   On Linux:
   $ getconf ARG_MAX
   2097152
   $ LC_ALL=C xargs --show-limits
   Your environment variables take up 4744 bytes
   POSIX upper limit on argument length (this system): 2090360
   POSIX smallest allowable upper limit on argument length (all systems): 4096
   Maximum length of command we could actually use: 2085616
   Size of command buffer we are actually using: 131072

   On FreeBSD/x86_64:
   $ getconf ARG_MAX
   262144
   $ LC_ALL=C xargs --show-limits
   Your environment variables take up 353 bytes
   POSIX upper limit on argument length (this system): 259743
   POSIX smallest allowable upper limit on argument length (all systems): 4096
   Maximum length of command we could actually use: 259390
   Size of command buffer we are actually using: 131072

   On macOS:
   $ getconf ARG_MAX
   262144
   $ LC_ALL=C xargs --show-limits
   Your environment variables take up 1262 bytes
   POSIX upper limit on argument length (this system): 258834
   POSIX smallest allowable upper limit on argument length (all systems): 4096
   Maximum length of command we could actually use: 257572
   Size of command buffer we are actually using: 131072

   How about being conservative and dividing the limit by 2, to avoid
   this margin error?

Could it be that your patch works only because xargs uses a command buffer
of length 131072, regardless of the value you pass to '-n'?

Bruno

[1] 
https://www.cyberciti.biz/faq/linux-unix-arg_max-maximum-length-of-arguments/