Well, in my real case this happens even with out-of-source builds, which
also occurs in the test case if I change:
set (OUT ${CMAKE_BINARY_DIR}/ext)
in ext/CMakeLists.txt.
Sure, I can avoid it by renaming the file or target, but I thought this
is something that could be avoided by either (a) generating unique ninja
target names when possible, or (b) warning at the cmake stage that
target names are duplicated.
From my point of view as a CMake user, I see no reason why the
combination of add_custom_command and add_custom_target should have a
conflict.
On 05/05/17 14:22, Robert Maynard wrote:
Hi,
This is caused by doing an in source build and thereby causing the
issue. The custom command is outputting a file called 'foo', which is
also the chosen name of a target in the ninja file. All of this results
in ninja conflating the two and causing a circular dependency.
Your options are to not to in source builds, or to choose a different
name for your custom target.
On Thu, May 4, 2017 at 3:55 AM, Ignacio Fernández Galván via CMake
<cmake@cmake.org <mailto:cmake@cmake.org>> wrote:
Hello,
I have a project where circular dependencies are generated when I
use the Ninja generator, but not the default Unix Makefiles. I could
create a minimal test like this:
$ cat CMakeLists.txt
add_subdirectory (ext ${PROJECT_BINARY_DIR}/ext)
$ cat ext/CMakeLists.txt
set (OUT ${CMAKE_CURRENT_LIST_DIR})
add_custom_command (OUTPUT ${OUT}/foo
COMMAND touch ${OUT}/foo
)
add_custom_target (foo ALL
DEPENDS ${OUT}/foo
)
add_custom_command (TARGET foo
POST_BUILD
COMMAND cp ${OUT}/foo ${CMAKE_BINARY_DIR}/foo
)
$ touch ext/bar
$ cmake -G Ninja .
[...]
$ ninja
ninja: warning: multiple rules generate ext/foo. builds involving
this target will not be correct; continuing anyway [-w dupbuild=warn]
ninja: error: dependency cycle: ext/foo -> ext/CMakeFiles/foo.util
-> ext/CMakeFiles/foo -> ext/foo
I used a freshly compiled CMake 3.8 and the latest binary ninja from
https://github.com/Kitware/ninja/releases
<https://github.com/Kitware/ninja/releases>.
Ignacio
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