[CMake] Inter-target dependencies on autogenerated headers

[Roger Leigh]

On Wed, Dec 18, 2013 at 11:54:15PM +0000, Roger Leigh wrote:
>   set(a_static_headers …)
>   set(b_static_sources …)
>   add_custom_command(OUTPUT ${a_generated_headers}
> ${a_generated_sources} COMMAND ${custom_tool} DEPENDS
> ${tool_dependencies)
>   set(a_headers ${a_generated_headers} ${a_static_headers})
>   set(a_sources ${a_generated_sources} ${a_static_sources})
>   add_library(a SHARED ${a_sources} ${a_headers})
> 
> Module b:
>   set(b_headers …)
>   set(b_sources …)
>   add_library(b SHARED ${b_sources} ${b_headers})
>   target_link_libraries(b a)
> 
> The code generation, compiling and linking of module a works fine,
> and the code is regenerated if the dependencies are touched.  This
> works building serially or in parallel.
> 
> The compiling and linking of module b works fine only if building
> serially.  If building in parallel, the ${b_sources} which include
> any headers from module a's ${a_generated_headers} will fail if they
> are built before header generation in module a occurs.  This is
> inherently racy.

Sorry for the noise, I found that I did in fact have some missing
target_link_libraries in some autogenerated tests (too much
autogeneration going on...).  Adding target_link_libraries for
everything fixes the dependencies and parallel building then
works just fine.


Regards,
Roger

-- 
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