* Passing c blocks to pre processor
@ 2022-05-28 5:48 Yair Lenga
2022-05-28 7:40 ` Jonathan Wakely
0 siblings, 1 reply; 2+ messages in thread
From: Yair Lenga @ 2022-05-28 5:48 UTC (permalink / raw)
To: gcc
Hi,
I am trying to define macros that will accept code blocks. This will be used to create high level structures (like iterations, etc.). Ideally, I would like to do something like (this is simplified example, actual code much more application specific):
Foreach(var, low, high, block)
While should translate to:
For (int var=low ; var < high ; var ++) block
The challnge is the gcc pre processor does not accept blocks. It assume a comma terminate a block. For example:
Foreach(foo, 1, 30, { int z=5, y=3, …}) will invoke the macro with 5 arguments: (1) foo (2) 1, (3) 30, (4) { int z=5}, (5) y=3,
Is there a way to tell CPP that an argument that start with ‘{‘ should extend until the matching ‘}’ ? Similar to the way ‘(‘ in macro arguments will extend till matching ‘)’.
Thanks, yair.
Sent from my iPad
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Passing c blocks to pre processor
2022-05-28 5:48 Passing c blocks to pre processor Yair Lenga
@ 2022-05-28 7:40 ` Jonathan Wakely
0 siblings, 0 replies; 2+ messages in thread
From: Jonathan Wakely @ 2022-05-28 7:40 UTC (permalink / raw)
To: Yair Lenga; +Cc: gcc
On Sat, 28 May 2022, 06:49 Yair Lenga via Gcc, <gcc@gcc.gnu.org> wrote:
> Hi,
>
> I am trying to define macros that will accept code blocks. This will be
> used to create high level structures (like iterations, etc.). Ideally, I
> would like to do something like (this is simplified example, actual code
> much more application specific):
>
> Foreach(var, low, high, block)
>
> While should translate to:
> For (int var=low ; var < high ; var ++) block
>
> The challnge is the gcc pre processor does not accept blocks. It assume a
> comma terminate a block. For example:
> Foreach(foo, 1, 30, { int z=5, y=3, …}) will invoke the macro with 5
> arguments: (1) foo (2) 1, (3) 30, (4) { int z=5}, (5) y=3,
>
> Is there a way to tell CPP that an argument that start with ‘{‘ should
> extend until the matching ‘}’ ? Similar to the way ‘(‘ in macro arguments
> will extend till matching ‘)’.
>
This question seems off-topic on this mailing list, as it's not about GCC
development. It would be more suited to the gcc-help list.
I don't think you can do that. You need to use __VA_ARGS__ to accept
arbitrary code containing commas. You could look at how the
Boost.Preprocessor library works.
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