[CMake] macro/function and ARGN weird behavior

[Nicolas Desprès]

Thx for the explanation David. I will take care of it.

Cheers,

2009/5/15 David Cole <david.cole at kitware.com>:
> The other difference (besides scoping) between a macro and a function
> explains the behavior you are seeing:
> The parameters to a function are automatically local variables inside the
> function scope. The parameters to a macro are not actually variables. They
> are merely expanded *as if* they were variables anywhere you see the ${}
> de-referencing syntax. Think of it like #define in C++ : the arguments are
> substituted where they are referenced, but they are not actually local
> variables.
>
> It's equivalent to the difference between these in C++:
> // there are not actually variables named x and y here:
> #define min(x, y) ......
> // but there are variables here:
> int min(int x, int y)
> {
>  .......
> }
>
> HTH,
> David
>
>
> 2009/5/15 Nicolas Desprès <nicolas.despres at gmail.com>
>>
>> Hi there,
>>
>> I'm experiencing a weird behavior with cmake 2.6.4 (Win32) playing
>> with macro, function and ARGN.
>>
>> === script
>> function(print_var)
>>  foreach(i ${ARGV})
>>    message("${i}='${${i}}'")
>>  endforeach(i)
>> endfunction(print_var)
>>
>> macro(print_var_macro)
>>  foreach(i ${ARGV})
>>    message("macro ${i}='${${i}}'")
>>  endforeach(i)
>> endmacro(print_var_macro)
>>
>> function(foo a1 a2)
>>  message("begin foo")
>>  message("a1=${a1}")
>>  message("a2=${a2}")
>>  message("ARGN=${ARGN}")
>>  print_var(a1 a2 ARGN) # 1
>>  print_var_macro(a1 a2 ARGN) # 2
>>  message("end foo")
>> endfunction(foo)
>>
>> macro(bar a1 a2)
>>  message("begin bar")
>>  message("a1=${a1}")
>>  message("a2=${a2}")
>>  message("ARGN=${ARGN}")
>>  print_var(a1 a2 ARGN) # 3
>>  print_var_macro(a1 a2 ARGN) # 4
>>  message("end bar")
>> endmacro(bar)
>>
>> foo("a" "b" "c" "d" "e")
>> bar("a" "b" "c" "d" "e")
>> === end script
>> === output
>> begin foo
>> a1=a
>> a2=b
>> ARGN=c;d;e
>> a1='a'
>> a2='b'
>> ARGN='a1;a2;ARGN'
>> macro a1='a'
>> macro a2='b'
>> macro ARGN='c;d;e'
>> end foo
>> begin bar
>> a1=a
>> a2=b
>> ARGN=c;d;e
>> a1=''
>> a2=''
>> ARGN='a1;a2;ARGN'
>> macro a1=''
>> macro a2=''
>> macro ARGN=''
>> end bar
>> === end output
>>
>> 1) I undestand it perfectly. ARGN is interpreted in the context of the
>> `print_var' function.
>> 2) I don't understand why the behavior is not similar to #1
>> 3) I don't understand why `a1' and `a2' are "eaten"
>> 4) This one is very weird.
>>
>> I though the only difference between macro and function was that
>> variables are scoped in a function and not in a macro. In all cases, I
>> find those behavior weird compared to what I'm used to in other
>> languages.
>>
>> Any light?
>>
>> Cheers,
>>
>> --
>> Nicolas Desprès
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the CMake FAQ at:
>> http://www.cmake.org/Wiki/CMake_FAQ
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.cmake.org/mailman/listinfo/cmake
>
>



-- 
Nicolas Desprès