[CMake] [Digital Signature Failure] Re: Hard to do if in Macro

[Dvir Yitzchaki]

You can add PARENT_SCOPE to set command to set the value on the calling code.

Regards,
Dvir

From: CMake [mailto:cmake-bounces at cmake.org] On Behalf Of J Decker
Sent: Tuesday, January 30, 2018 18:07
To: Petr Kmoch <petr.kmoch at gmail.com>
Cc: CMake Mail List <cmake at cmake.org>
Subject: [Digital Signature Failure] Re: [CMake] Hard to do if in Macro

Okay... but then with function I can't set external variables; but if( __ANDROID__ ) works.

`result` never changes.

---------------------------

set( __ANDROID__ 1 )

function( test __ANDROID__ RETVAL )

  if( ${__ANDROID__} EQUAL 1 OR ${__ANDROID__} STREQUAL "ON")
    set( ${RETVAL} ${${RETVAL}} qwer2 )
    message( "Included..... " )
  endif( ${__ANDROID__} EQUAL 1 OR ${__ANDROID__} STREQUAL "ON")

  if( __ANDROID__ )
    set( ${RETVAL} ${${RETVAL}} asdf )
    message( "ALWAYS Included ${__ANDROID__}" )
  endif( __ANDROID__ )

endfunction( test )


set( result "default" )

test( __ANDROID__ "result" )
message( "REsult:${result}" )

test( ${__ANDROID__} "result" )
message( "REsult:${result}" )

test( OFF  "result")
message( "REsult:${result}" )

---------------------------




On Tue, Jan 30, 2018 at 12:35 AM, Petr Kmoch <petr.kmoch at gmail.com<mailto:petr.kmoch at gmail.com>> wrote:
Macros aren't functions, and macro parameters aren't CMake variables. Expanding a macro parameter is effectively *textual* substitution, whereas dereferencing a CMake variable is a semantic one.
In other words, inside your macro, the text __ANDROID__ (when not expanded) never refers to the macro parameter. Macro parameters "don't exist" outside of expansion context. The `if(__ANDROID__)` bit therefore always refers to the variable __ANDROID__, never to the macro parameter __ANDROID__.
You still don't have to spell out the conditional as explicitly as you're doing it now, but you have to expand the parameter:
macro(test __ANDROID__)
  if(${__ANDROID__})
    message( "Included..... " )
  endif()
endmacro()
This is what the evaluation will look like based on how you call it:
test(__ANDROID__)   -> if(__ANDROID__) -> refers to the variable
set(__ANDROID__ 1)
test(${__ANDROID__})   -> if(1)
set(__ANDROID__ 0)
test(${__ANDROID__})   -> if(0)
test(OFF)   -> if(OFF)
CMake macros have a lot of specific and potentially weird/counterintuitive behaviour. In general, you should always write your commands as functions and only resort to macros if you explicitly need their specific behaviour.
Petr



On 30 January 2018 at 09:11, J Decker <d3ck0r at gmail.com<mailto:d3ck0r at gmail.com>> wrote:
Why do I have to do

if( ${M__ANDROID__} EQUAL 1 OR ${M__ANDROID__} STREQUAL "ON")
endif( ${M__ANDROID__} EQUAL 1 OR ${M__ANDROID__} STREQUAL "ON")

in a macro like...
----------------------

set( __ANDROID__ 1 )

macro( test __ANDROID__ )

  if( ${__ANDROID__} EQUAL 1 OR ${__ANDROID__} STREQUAL "ON")
    message( "Included..... " )
  endif( ${__ANDROID__} EQUAL 1 OR ${__ANDROID__} STREQUAL "ON")

  if( __ANDROID__ )
    message( "ALWAYS Included ${__ANDROID__}" )
  endif( __ANDROID__ )

endmacro( test )

test( __ANDROID__ )
test( ${__ANDROID__} )
test( OFF )

----------
Output

Included.....
ALWAYS Included __ANDROID__
Included.....
ALWAYS Included 1
ALWAYS Included OFF

--

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