Why one target produces expected output and another target which depends on the first one does not produce any output?

[Konstantin Erman]

I am trying to write a macro to build Windows shared libraries (DLL) based on this example: https://github.com/bazelbuild/bazel/tree/master/examples/windows/dll

 

When I run “bazel build //examples/windows/dll:hello_world-link-to-dll-via-lib” I get the result expected – out folder contains hellolib.dll and import library hellolib.dll.if.lib.

 

But when I try to just build the DLL target specifically with “bazel build //examples/windows/dll:hellolib” I get nothing – empty out folder.

 

Interestingly “bazel build //examples/windows/dll:hellolib.dll” produces DLL and the import library as expected.

 

This is very confusing, why the target “:hellolib.dll” produces the output and the target “:hellolib” which depend on the target “:hellolib.dll” does not produce the output.

 

Can anybody comment?

 

Konstantin

 

[László Csomor]

Hi Konstantin,

This looks like a cc_library + cc_import combination bug. Could you
please report it on GitHub? (https://github.com/bazelbuild/bazel/issues/new)

I can repro it on Linux too:

# Build the shared library
cc_binary(
name = "foo.so",
srcs = ["foo.cc", "foo.h"],
linkshared = 1,
#copts = ["/DCOMPILING_DLL"],
copts = ["-fPIC"],
)

# Get the import library for the dll
filegroup(
name = "foo_imp_lib",
srcs = [":foo.so"],
output_group = "interface_library",
)

# Because we cannot directly depend on cc_binary from other cc
# rules in deps attribute, we use cc_import as a bridge to depend
# on the dll.
cc_import(
name = "foo_import",
interface_library = ":foo_imp_lib",
shared_library = ":foo.so",
)

# Create a new cc_library to also include the headers needed for
# the shared library
cc_library(
name = "foo",
hdrs = ["foo.h"],
deps = [":foo_import"],
)

Building ":foo" does not compile or link anything, but building
"foo_imp_lib" does.


--
László Csomor | Software Engineer | laszlo...@google.com

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[Konstantin Erman]

Thank you, László! Issue opened: https://github.com/bazelbuild/bazel/issues/10770

Konstantin