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Re: Preprocessor <-> compiler

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On 03/10/2021 20:16, Thiago Adams wrote:
> On Sunday, October 3, 2021 at 3:41:24 PM UTC-3, Bart wrote:

>>> -#pragma are used to control the compiler. what happen using an external preprocessor
>>> will just remove the content?
>> If an implementation doesn't understand what follows #pragma, then it
>> will just ignore it.
> 
> Yes but if you think a traditional preprocessor that runs before and generate a file that
> latter will be the input for the compiler then the #pragma is removed (empty line) when the file
> is printed and the compiler will not have access to it.

No, I said the compiler keeps it in. (Well, I tried gcc, tcc, clang and 
lccwin which did, and bcc which didn't.)

Probably precisely for that reason.

> 

> yes... this is why it is funny. it is like a macro expansion by the compiler.

In my language this stuff is done by the parser anyway.

> If the information required by the preprocessor from the compiler is
> static then everything is easy. sizeof(int) for instance could be
> implemented easily if necessary, but sizeof(variable) not.

sizeof(int) maybe, but probably not sizeof(int32_t). First this will 
require headers to be present, that's OK, but int32_t is likely to be a 
typedef.

However this rings a bell ... yes, I've put sizeof() into my own 
preprocessor, so that this is possible:

   #if sizeof(int) == 4

but with the aforementioned problems using int32_t.

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Preprocessor <-> compiler Thiago Adams <thiago.adams@gmail.com> - 2021-10-03 06:47 -0700
  Re: Preprocessor <-> compiler Thiago Adams <thiago.adams@gmail.com> - 2021-10-03 08:38 -0700
  Re: Preprocessor <-> compiler Bart <bc@freeuk.com> - 2021-10-03 17:24 +0100
    Re: Preprocessor <-> compiler Thiago Adams <thiago.adams@gmail.com> - 2021-10-03 10:55 -0700
      Re: Preprocessor <-> compiler Bart <bc@freeuk.com> - 2021-10-03 19:41 +0100
        Re: Preprocessor <-> compiler Thiago Adams <thiago.adams@gmail.com> - 2021-10-03 12:16 -0700
          Re: Preprocessor <-> compiler Bart <bc@freeuk.com> - 2021-10-03 20:28 +0100
            Re: Preprocessor <-> compiler Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-03 14:12 -0700
  Re: Preprocessor <-> compiler Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-10-06 08:41 -0700
    Re: Preprocessor <-> compiler Thiago Adams <thiago.adams@gmail.com> - 2021-10-06 10:56 -0700

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