The "loop and a half"

[Ben Bacarisse]

bartc <bc at freeuk.com> writes:

> On 06/10/2017 14:35, Paul Moore wrote:
>> On 6 October 2017 at 13:56, bartc <bc at freeuk.com> wrote:
>>> If you don't like the word 'crude', try 'lazy'. Take this example of the gcc
>>> C compiler:
>>>
>>>   > gcc -E program.c
>>>
>>> This preprocesses the code and shows the result. Typical programs will have
>>> many thousands of lines of output, but it just dumps it to the console. You
>>> /have/ to use '>' to use it practically (Windows doesn't really have a
>>> working '|' system.)

Does the Windows version of gcc not support the -o file option?

>> No you don't. Ignoring the fact that "windows doesn't really have a
>> working '|' system" (which is an oversimplification, by the way) the
>> following all work:
>>
>> Python:
>>      data = subprocess.check_output(["gcc", "-E", "program.c"])
>> Powershell:
>>      $x = (gcc -E program.c)
>> cmd:
>>      for /f %i in ('gcc -E program.c') do ...
>>
>> If gcc -E wrote its output to a file, you'd have to read that file,
>> manage the process of deleting it after use (and handle possible
>> deletion of it if an error occurred), etc.
>
> But if I use the -S option (show assembly listing) that DOES output to
> a file (program.s).

And a good system lets you alter that.  How many labels are generated
for some code?  Let's see:

  gcc -S -o /dev/stdout t.c | grep -c '^\.L'

Now gcc also permits -o - (it's a common Unix convention) but you can
almost always get round less helpful programs using /dev/sdout.

<snip>
-- 
Ben.