[cmake-developers] Should sucessive calls to find_package for one package succeed?

2011-11-06 Thread Stephen Kelly 

Hi,

Should successive calls to find_package succeed in general?

Eg 

find_package(Grantlee COMPONENTS Templates)
find_package(Grantlee COMPONENTS TextDocument)

?

Currently if the target package uses Config files and 

install(TARGETS ... EXPORT)

the convention is to use

include(${CMAKE_CURRENT_LIST_DIR}/GrantleeTargets.cmake)

in the config file. The problem is that that Targets file uses an unguarded 

ADD_LIBRARY(grantlee_templates SHARED IMPORTED)

which cmake errors on:

  add_library cannot create imported target "grantlee_templates" because 
another target with the same name already exists.

The fix appears to be to wrap the call to add_library:

if (NOT TARGET grantlee_templates)
  ADD_LIBRARY(grantlee_templates SHARED IMPORTED)
endif()

I can fix this if it is a bug.

Thanks,

Steve.


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Re: [cmake-developers] Should sucessive calls to find_package for one package succeed?

2011-11-07 Thread Brad King 

On 11/6/2011 7:00 PM, Stephen Kelly wrote:

include(${CMAKE_CURRENT_LIST_DIR}/GrantleeTargets.cmake)


It is up to the author of the config file to block this correctly
against multiple inclusion, e.g.

 if(NOT Grantlee_TARGETS_INCLUDED)
   set(Grantlee_TARGETS_INCLUDED 1)
   include(${CMAKE_CURRENT_LIST_DIR}/GrantleeTargets.cmake)
 endif()


if (NOT TARGET grantlee_templates)
   ADD_LIBRARY(grantlee_templates SHARED IMPORTED)
endif()


This would hide cases of accidentally conflicting target names.

-Brad
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Re: [cmake-developers] Should sucessive calls to find_package for one package succeed?

2011-11-07 Thread Stephen Kelly 
Brad King wrote:

> On 11/6/2011 7:00 PM, Stephen Kelly wrote:
>> include(${CMAKE_CURRENT_LIST_DIR}/GrantleeTargets.cmake)
> 
> It is up to the author of the config file to block this correctly
> against multiple inclusion, e.g.
> 
>   if(NOT Grantlee_TARGETS_INCLUDED)
> set(Grantlee_TARGETS_INCLUDED 1)
> include(${CMAKE_CURRENT_LIST_DIR}/GrantleeTargets.cmake)
>   endif()

Ok, thanks. Seems like an important thing to document. Is there any page 
showing how to use config files and targets files? I only found out how to 
use them by talking to Alex :).

> 
>> if (NOT TARGET grantlee_templates)
>>ADD_LIBRARY(grantlee_templates SHARED IMPORTED)
>> endif()
> 
> This would hide cases of accidentally conflicting target names.
> 

I don't understand. You mean if someone called install(EXPORTS) with the 
wrong target? 

Thanks,

Steve.




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Re: [cmake-developers] Should sucessive calls to find_package for one package succeed?

2011-11-07 Thread Brad King 

On 11/7/2011 10:18 AM, Stephen Kelly wrote:

Ok, thanks. Seems like an important thing to document. Is there any page
showing how to use config files and targets files?


http://www.cmake.org/Wiki/CMake/Tutorials#CMake_Packages

This section:

  http://www.cmake.org/Wiki/CMake/Tutorials/Packaging#Packaging_and_Exporting

could be updated with that suggestion.


if (NOT TARGET grantlee_templates)
ADD_LIBRARY(grantlee_templates SHARED IMPORTED)
endif()


This would hide cases of accidentally conflicting target names.


I don't understand.


If an application defines a target named "foo" as part of its own build
and then uses find_package to load a dependency that also defines "foo"
then a target-wise blocker like the above will silently skip the imported
target.  Then the imported dependency won't link correctly because it
will use the application's foo instead of the package's foo.  We need to
allow the add_library command to complain about an existing target.

-Brad
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