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

From: Eric Blake
Subject: Re: [Qemu-trivial] [PATCH v4] tests: Avoid non-portable 'echo -ARG'
Date: Tue, 8 Aug 2017 09:29:58 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 08/08/2017 08:54 AM, Kevin Wolf wrote:
> Am 03.07.2017 um 20:09 hat Eric Blake geschrieben:
>> POSIX says that backslashes in the arguments to 'echo', as well as
>> any use of 'echo -n' and 'echo -e', are non-portable; it recommends
>> people should favor 'printf' instead.  This is definitely true where
>> we do not control which shell is running (such as in makefile snippets
>> or in documentation examples).  But even for scripts where we
>> require bash (and therefore, where echo does what we want by default),
>> it is still possible to use 'shopt -s xpg_echo' to change bash's
>> behavior of echo.  And setting a good example never hurts when we are
>> not sure if a snippet will be copied from a bash-only script to a
>> general shell script (although I don't change the use of non-portable
>> \e for ESC when we know the running shell is bash).

>> +++ b/tests/multiboot/run_test.sh
>> @@ -26,7 +26,7 @@ run_qemu() {
>>      local kernel=$1
>>      shift
>> -    echo -e "\n\n=== Running test case: $kernel $@ ===\n" >> test.log
>> +    printf %b "\n\n=== Running test case: $kernel $@ ===\n\n" >> test.log
>>      $QEMU \
>>          -kernel $kernel \
> 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?

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 $*.

Fix coming up.

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

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