CODEWITHSUNDEEP
c++cmakecompilationbuild-system
Hassan Syed
Hassan Syed

Reputation: 20485

CMAKE: Creating and building a list within a function -- with directory, or global scope

I am not entirely familiar with the scoping rules of cmake. I need to buildup a list of various files whilst doing RPC code-generation for an IDL.

function(generate_rpc file_name)
  set(PROTO_FILES ${PROTO_FILES} ${file_name})
endfunction(generate_rpc)

generate_rpc(BasicProtocol.proto)
generate_rpc(dummy.proto)

message(STATUS "PROTO FILES: ${PROTO_FILES}")

The list is empty each time. I need append-able list that can be built from within a function.

Upvotes: 11

Views: 7851

Answers (2)

uelordi
uelordi

Reputation: 2209

Although Macros are defined and called in the same manner as functions, there are some differences between them, for example in SCOPE and when its execution.

SCOPE:

  • Macro: has global scope.
  • Function: has a local scope whether you don't specify.

EXECUTION: it works like C++ or C

  • Macro: the variable names are replaced to strings before configuring.

  • Function: the variable names are replaced during execution.

In conclusion, add the PARENT_SCOPE flag in set command

set(PROTO_FILES ${PROTO_FILES} ${file_name} PARENT_SCOPE)

Upvotes: 11

tibur
tibur

Reputation: 11636

Using a macro instead of a function seems to do it:

macro(generate_rpc file_name)
  set(PROTO_FILES ${PROTO_FILES} ${file_name})
endmacro(generate_rpc)

EDIT: According to http://www.cmake.org/cmake/help/syntax.html (should be in the man page, IMO):

CMake functions create a local scope for variables, and macros use the global scope.

Upvotes: 11

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