commit 916f4e513cdf1fb6adec3d8898014550fa45c315
author Primiano Tucci <primiano@google.com> Fri Oct 16 20:40:33 2020 +0200
committer Primiano Tucci <primiano@google.com> Fri Oct 16 20:40:33 2020 +0200
tree 80df2bc9d75dbe0a5b29a15e50782977aff5898a
parent 8065f31f44ea3f3e671a3ce04db584f569cbb526

Remove ODR violations from Bazel builds

The process of generating Bazel build files
from GN caused ODR violations when flattening GN
source_set(s) into file groups.
The problem is the following: file groups are effectively
just list of source paths. Unlike GN, where the build
system retains the identity of the source_set, using
the same source_set in different targets causes the
same sources to get compiled and linked multiple times.
So in Bazel and SoonG we have two conflicting needs:
1. We can only depend on static_library targets. One
   can not depend on a filegroup in Bazel. This
   is the reason why "protozero" exists as a static
   library in Bazel builds: we need the generated
   protobuf sources to be able to depend on a target
   and that target becomes a static_library.
2. By flattening and propagating up source sets as
   filegroups we end up with the same filegroup being
   linked in several different static libraries.

Note that the same situation exists in SoonG. There,
however things are more complicated because heapprofd_client
depends on base but wants to build it with different cflags
(-DPERFETTO_ANDROID_ASYNC_SAFE_LOG) so we can't split that
into a static_library yet.

The root problem here was the following:
libperfetto_client_experimental(static_lib) ->  libprotozero(static_lib) -> base(filegroup)
libperfetto_client_experimental(static_lib) -> perfetto_ipc(static_lib) -> base(filegroup)

This CL fixes it by making base a static_library.
Furthermore this adds a test at the tools/gen_xxx level to
avoid regressing this in future.

Bug: 154625868
Test: built into tools/gen_android_bp and tools/gen_bazel
Change-Id: I80004c64e571bd85f9791673ee7740a088989dcc