Bazel basics

Everything happens under your drake/ folder.

cd drake

Build

To build the whole folder:

bazel build //...

bazel build takes all available CPUs to compile. The compilation would fail if not enough memory is available. To limit the number of concurrent tasks, use bazel build //... --jobs=n , where n is the number of CPUs used.

// means the root path of your drake folder, it equals drake/. ... means build everything. Build everything can take a long time. We can speed up the building by narrowing down to a subfolder. For example, to build all targets under a subfolder:

bazel build //tools/...

Or to build a specific target:

bazel build //tools:drake_visualizer

//tools tells bazel that the path of the target is drake/tools/. What's followed after : is the target drake_visualizer. bazel will find the BUILD.bazel file under drake/tools/ and build the target based on the rules defined in the BUILD.bazel.

Run

To run a specific executable:

bazel run //examples/double_pendulum:double_pendulum_demo

bazel run will detect the relevant file modification. If the files are changed, this command will build first and then run immediately after the build. : is followed by the executable binary, in this case, double_pendulum_demo.

Another way to run the binary is to type the binary name directly in the terminal. It does not check the file change nor recompile. All the bazel binaries are put in the drake/bazel-bin/ folder after being built. The detailed location of an executable is defined by BUILD.bazel.

bazel-bin/examples/double_pendulum/double_pendulum_demo

How to find where is the executable? Well, check the BUILD.bazel file and find the drake_cc_binary item. The executable sits in the name line.

Debug

using gdb to debug when you find errors like segmentation fault comes handy. We could compile the executable with gdb by:

bazel build --compilation_mode=dbg //examples/multibody/inclined_plane_with_body

Then you could run the executable with gdb inspecting the variables and function calls. When there is a error and program crashes, we could trace back to where it went wrong.

gdb ./bazel-bin/examples/multibody/inclined_plane_with_body
(gdb) run # execute the program and record the runtime stack data
(gdb) bt # back trace to where the program crashes and figure the problem
(gdb) quit

Test

This command applies when you wrote your own function and test cases. Then you could test your cases by:

bazel test //common:polynomial_test

For more bazel commands

Commands in this page are enough to handle most cases.

For advanced bazel usage, check out the Drake document of bazel.

To learn more about bazel, please refer to bazel official document.

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