I am starting to use Bazel as my C++ project build system.
However I am stuck with the following problem:
I am in a scenario where I automatically generate the file.hpp file.cpp (literate programming).
To reproduce my problem one can simply use this minimal generator:
-- file.sh --
#!/bin/sh
echo "int foo();" >> file.hpp
echo "#include \"myLib/file.hpp\"\n\nint foo() { return 2017; }" >> file.cpp
My project repo is: (WORKSPACE is an empty file)
├── myLib
│ ├── BUILD
│ └── file.sh
└── WORKSPACE
The BUILD file is
genrule(
name = "tangle_file",
srcs = ["file.sh"],
outs = ["file.cpp","file.hpp"],
cmd = "./$(location file.sh);cp file.cpp $(@D);cp file.hpp $(@D);"
)
cc_library(
name = "file",
srcs = ["file.cpp"],
hdrs = ["file.hpp"],
# deps = [":tangle_file"],
visibility = ["//bin:__pkg__"],
)
I have two problems:
Question (A), dealing with the genrule() part:
The fact that I must use
cmd = "./$(location file.sh);cp file.cpp $(@D);cp file.hpp $(@D);"
is quite mysterious.
My first attempt was:
cmd = "./$(location file.sh)"
However in that case I get the following error:
declared output 'myLib/file.cpp' was not created by genrule. This is probably because the genrule actually didn't create this output, or because the output was a directory and the genrule was run remotely (note that only the contents of declared file outputs are copied from genrules run remotely)
Question (B), dealing with the cc_library() part
I do not know how to make Bazel aware of that the :file target depends on the :tangle_file target.
If I uncomment:
deps = [":tangle_file"],
I get the following error:
in deps attribute of cc_library rule //myLib:file: genrule rule '//myLib:tangle_file' is misplaced here (expected cc_inc_library, cc_library, objc_library, experimental_objc_library or cc_proto_library).