Re: [Qemu-devel] [PATCH v4] tests: Avoid non-portable 'echo -ARG'

[Eric Blake]

On 08/08/2017 09:48 AM, Kevin Wolf wrote:

>>> Not completely sure why, but this broke the test with whitespace changes
>>> like this:
>>>
>>> -=== Running test case: mmap.elf -m 1.1M ===
>>> +=== Running test case: mmap.elf -m1.1M ===
>>
>> I guess that means I'm not regularly running tests/multiboot?  Is it not
>> part of 'make check' or qemu-iotests?
> 
> The problem is that it needs an i386 compiler to build the test kernels
> (and qemu-system-i386 or qemu-system-x86_64 binaries to execute them).
> 
> I guess we could check these conditions, though, and skip the test if we
> can't produce i386 binaries.

And when you CAN run the test, it litters 'git status' of an in-tree
build with:

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        tests/multiboot/mmap.elf
        tests/multiboot/modules.elf
        tests/multiboot/test.out

which ought to be fixed.

> 
>> Ah, I see the problem, and it's insidious.  We're using "address@hidden", but
>> want to be using "...$*...".  $@ causes multiple arguments to be passed,
>> but printf %b is not concatenating those arguments; while $* uses only a
>> single argument.  We didn't notice it with echo -e, because echo inserts
>> a space between multiple arguments, just as you'd get a space with $*.
> 
> The thing that completely confused me here is that printf doesn't just
> ignore additional arguments as I would have expected, but just starts
> over with the format string, so that it does kind of work with multiple
> arguments and fails only subtly.

Both echo and printf accept more than one argument, but only echo
injects an automatic space between those arguments in the output.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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