[Buildroot] [PATCH 2/2] mke2img: add parameter sanity checks to prevent odd error messages from genext2.fs

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2017-04-29 21:06 +0200, Thomas Petazzoni spake thusly:
> Hello,
> 
> On Sat, 29 Apr 2017 17:01:22 +0100, J Evans wrote:
> 
> > +    if [ -z "${nb_blocks}" ]; then
> > +        error "Error: you must specify a file system block count with '-b'. This cannot be zero, e.g. 61440 == 60MB\n"

Really, just state that it must be specified, this the value is
explained in the help text.

    error "Error: you must specify a file system block count with '-b'.\n"

However, please also update the help text at the end of the script,m to
remove a hint about auto calculation:

    https://git.buildroot.org/buildroot/tree/package/mke2img/mke2img#n152

    -b BLOCKS
        Create a filesystem of BLOCKS 1024-byte blocs. The default is to
        compute the required number of blocks.

> > +    fi
> 
> Check this is useless: there is already error checking done by getopt
> itself, because the -b option *must* have an argument. Indeed, the
> current mke2img behaves like this:
> 
> $ ./package/mke2img/mke2img -b
> mke2img: option 'b' expects a mandatory argument
> 
> So it is already checked that ${nb_blocks} cannot be empty.

But if you don't pass the -b option, then nb_blocks *is* unset.

Adding the check is correct in my opinion.

> > +    if [ "${nb_blocks}" -eq 0 ]; then
> > +        error "Error: The file system block count size cannot be zero. e.g. 61440 == 60MB \n"
> > +    fi
> 
> See my reply to the previous commit: I don't see why 0 should be
> checked specifically. Please explain in the commit log why it should be.

Agreed, a zero size is like specifying any size that is too small to fit
the content of target/. There is no way we can check that the given size
is correct.

zero if of course special, because we *know* it is incorrect. But since
this is not the default value, the user would have explicitly set it to
zero. Which is justa little tad stupid to begin with.

As I previously said: I really don't see the point of checking that the
size is not zero.

Just keep the text tht nb_blocks is set, though, because it is required.

Regards,
Yann E. MORIN.

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