Hi Peter,
We've come across a case where the Makefile, VS, and Xcode generators
work but Ninja does not::
cmake_minimum_required(VERSION 2.8.10)
project(DependSideEffect C)
add_library(A a.c)
add_custom_command(
TARGET A POST_BUILD
COMMAND cp ${CMAKE_CURRENT_SOURCE_DIR}/a.c a.txt
)
add_custom_command(
OUTPUT b.txt
DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/a.txt
COMMAND cp a.txt b.txt
)
add_custom_target(B ALL DEPENDS b.txt)
add_dependencies(B A)
CMake's rule for target-level dependencies is that "A" must be up to
date before the build system evaluates the rules of "B".
Building with Ninja fails with::
ninja: error: 'a.txt', needed by 'b.txt', missing and no known rule to make it
Relevant portions of build.ninja::
build libA.a: C_STATIC_LIBRARY_LINKER CMakeFiles/A.dir/a.c.o
POST_BUILD = cd ".../build" && cp .../a.c a.txt
...
build b.txt: CUSTOM_COMMAND a.txt || libA.a
COMMAND = cd ".../build" && cp a.txt b.txt
...
The rule for "b.txt" has an order-only dependency on "libA.a" and
an explicit dependency on "a.txt". Ninja does not wait for the
order-only dependencies to be up to date before complaining that
the explicit dependency is missing.
Can ninja be taught to wait for order-only dependencies to be up to
date to see if they produce any of the explicit dependencies as
a side effect? Is there another way to do this in CMake's Ninja gen?
Thanks,
-Brad
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