commit 3feec55302941c3b0d36275b4bfcf770a41060e4
author Primiano Tucci <primiano@google.com> Tue Feb 04 11:14:42 2020 +0000
committer Primiano Tucci <primiano@google.com> Tue Feb 04 11:14:42 2020 +0000
tree 7581f1d59d4cc3bfec0c41d466204bb1b968c659
parent 784967be4d56903b43b4bcaf2606bcb26be1597e

Client library: make code gc-sections friendly

The problem we want to solve is the following: on Android
some targets (e.g. libsurfaceflinger) rely on the system
backend for production code but then want the in-process
backend for tests. Both backends are big in terms of binary
size (~200 KB).
Instead of relying on dedicated build targets this code
arranges the build targets in a way that allows the linker to
dead-code-eliminate unused backends if the caller doesn't
require them.

Test: manual: the size of /system/lib64/libsurfaceflinger.so
      is == the size when completely removing the in-process
      target.
Bug: 148198993
Change-Id: Ie891a9b2e6ec38a3781318d1204a694899b01656

BUILD

diff --git a/BUILD b/BUILD
index e7a59ac..5c0cb4b 100644
--- a/BUILD
+++ b/BUILD
@@ -475,6 +475,8 @@
         "include/perfetto/tracing/event_context.h",
         "include/perfetto/tracing/internal/basic_types.h",
         "include/perfetto/tracing/internal/data_source_internal.h",
+        "include/perfetto/tracing/internal/in_process_tracing_backend.h",
+        "include/perfetto/tracing/internal/system_tracing_backend.h",
         "include/perfetto/tracing/internal/tracing_muxer.h",
         "include/perfetto/tracing/internal/tracing_tls.h",
         "include/perfetto/tracing/internal/track_event_data_source.h",
@@ -1220,15 +1222,13 @@
     ],
 )
 
-# GN target: //src/tracing:client_api_base
+# GN target: //src/tracing:client_api_without_backends
 filegroup(
-    name = "src_tracing_client_api_base",
+    name = "src_tracing_client_api_without_backends",
     srcs = [
         "src/tracing/data_source.cc",
         "src/tracing/debug_annotation.cc",
         "src/tracing/event_context.cc",
-        "src/tracing/internal/in_process_tracing_backend.h",
-        "src/tracing/internal/system_tracing_backend.h",
         "src/tracing/internal/tracing_muxer_impl.cc",
         "src/tracing/internal/tracing_muxer_impl.h",
         "src/tracing/internal/track_event_internal.cc",
@@ -1264,9 +1264,9 @@
     ],
 )
 
-# GN target: //src/tracing:system_process_backend
+# GN target: //src/tracing:system_backend
 filegroup(
-    name = "src_tracing_system_process_backend",
+    name = "src_tracing_system_backend",
     srcs = [
         "src/tracing/internal/system_tracing_backend.cc",
     ],
@@ -2479,7 +2479,7 @@
         ":src_ipc_common",
         ":src_ipc_host",
         ":src_protozero_protozero",
-        ":src_tracing_client_api_base",
+        ":src_tracing_client_api_without_backends",
         ":src_tracing_common",
         ":src_tracing_core_core",
         ":src_tracing_core_service",
@@ -2489,7 +2489,7 @@
         ":src_tracing_ipc_producer_producer",
         ":src_tracing_ipc_service_service",
         ":src_tracing_platform_posix",
-        ":src_tracing_system_process_backend",
+        ":src_tracing_system_backend",
     ],
     hdrs = [
         ":include_perfetto_base_base",