"No rule to make target" Error When Using make -j with cmake

Question

When I use "make -j" I get a "No rule to make target" error. When I use make (no -j), I don't get the error. The library is built as follows in one directory:

add_library(Environment ${CXXSRCS}

and libEnvironment.a is created. In another directory libEnvironment.a is referenced:

add_executable(GetEnv ${GETSRCS})
target_link_libraries(GetEnv
    ${tools_environment_SOURCE_DIR}/libEnvironment.a
    xml++-2.6
    )

When I run with "cmake -j", I get the error then the library gets created, but cmake stops. When I run cmake -j again, everything is happy because the library has been created. Any ideas?

Answer 1

当make -j正在使用时，除非一个目标明确设置为依赖另一个目标，否则任何目标都可以并行构建。

在您的情况下，您拥有GetEnv（可执行）目标，该目标使用由Environment（库）目标生成的文件。但是目标之间没有明确的依赖关系！

与库链接的正确（和最简单）方法是使用库目标名称而不是由该目标创建的库文件：

  

target_link_libraries（GetEnv 环境 xml ++ - 2.6）

这样一来，您就会在GetEnv和Environment目标之间产生依赖关系，因此make -j将不再尝试并行构建它们。