I have a Python script named blob_to_cpp.py (located at scirpts/blob_to_cpp.py relative to the WORKSPACE.bazel file). The Python script takes an input file (e.g. weights/rt_alb.tza) and generates from that a C++ header (.h) and source file (.cpp) that I want to add to a cc_binary.
The source code of my minimal reproducible example can be found here.
The Python script can be called via:
bazel run //:blob_to_cpp -- -o weights/rt_alb.cpp -H weights/rt_alb.h weights/rt_alb.tza
I try to use a genrule to invoke the python script (bazelized via py_binary as //:blob_to_cpp)
bazel/odin_generate_cpp_from_blob.bzl:
"""
SPDX-FileCopyrightText: 2023 Julian Amann <[email protected]>
SPDX-License-Identifier: Apache-2.0
"""
def generate_cpp_from_blob_cc_library(name, **kwargs):
native.genrule(
name = "%s_weights_gen" % name,
srcs = ["weights/" + name],
outs = [
"weights/" + name[0:-4] + ".cpp",
"weights/" + name[0:-4] + ".h",
],
cmd = "./$(location //:blob_to_cpp) weights/%s -o weights/%s.cpp -H weights/%s.h" % (name, name[0:-4], name[0:-4]),
tools = ["//:blob_to_cpp"],
)
native.cc_library(
name = name,
srcs = ["weights/" + name[0:-4] + ".cpp"],
hdrs = ["weights/" + name[0:-4] + ".h"],
**kwargs
)
When the generate_cpp_from_blob_cc_library Bazel macro is invoked I recive the following error messages (bazel build //:Demo):
ERROR: /Users/vertexwahn/dev/Piper/BazelDemos/intermediate/Cpp/BlobToCpp/BUILD.bazel:14:34: declared output 'weights/rt_alb.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)
ERROR: /Users/vertexwahn/dev/Piper/BazelDemos/intermediate/Cpp/BlobToCpp/BUILD.bazel:14:34: declared output 'weights/rt_alb.h' 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)
ERROR: /Users/vertexwahn/dev/Piper/BazelDemos/intermediate/Cpp/BlobToCpp/BUILD.bazel:14:34: Executing genrule //:rt_alb.tza_weights_gen failed: not all outputs were created or valid
Target //:Demo failed to build
My goal is to generate the files weights/rt_alb.cpp and weights/rt_alb.h. I need them in the weights folder since my cc_binary is expecting that the header file is within the weights folder (#include "weights/rt_alb.h").
My BUILD.bazel file looks like this:
load("//bazel:odin_generte_cpp_from_blob.bzl", "generate_cpp_from_blob_cc_library")
py_binary(
name = "blob_to_cpp",
srcs = ["scripts/blob_to_cpp.py"],
data = ["weights/rt_alb.tza"]
)
generate_cpp_from_blob_cc_library(
name = "rt_alb.tza"
)
cc_binary(
name = "Demo",
srcs = ["main.cpp"],
deps = [":rt_alb.tza"],
)
Any hints to get this working are welcome!
The problem
declared output 'weights/rt_alb.cpp' was not created by genrule
usually means the command in the genrule is putting the files someplace other than where bazel expects them. You can use $(location target) for inputs and outputs, as well as for tools:
# Copyright 2023 Google LLC.
# SPDX-License-Identifier: Apache-2.0
def generate_cpp_from_blob_cc_library(name, **kwargs):
src = "weights/" + name
cpp_out = "weights/" + name[0:-4] + ".cpp"
header_out = "weights/" + name[0:-4] + ".h"
native.genrule(
name = "%s_weights_gen" % name,
srcs = [src],
outs = [
cpp_out,
header_out,
],
cmd = ("./$(location //:blob_to_cpp) $(location {src}) " +
"-o $(location {cpp_out}) " +
"-H $(location {header_out})").format(
src = src,
cpp_out = cpp_out,
header_out = header_out),
tools = ["//:blob_to_cpp"],
)
native.cc_library(
name = name,
srcs = [cpp_out],
hdrs = [header_out],
**kwargs
)