move api and create dependent option

Move the C++ api files under a new subdirectory. Use CMAKE_DEPENDENT_OPTION to enforce sdt->cpp_api relationship. Since linking .a into a .so can cause global symbols to be dropped, add a helper file to force exported symbols to be retained (link_all.cc). This problem doesn't exist for building the static cpp examples. Signed-off-by: Brenden Blanco <[email protected]>
nanshuaibo · Aug 25, 2017 · 71fc3d5 · 71fc3d5
1 parent 1614ce7
commit 71fc3d5
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Showing 10 changed files with 38 additions and 5 deletions.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -11,6 +11,7 @@ enable_testing()
 
 include(cmake/GetGitRevisionDescription.cmake)
 include(cmake/version.cmake)
+include(CMakeDependentOption)
 include(GNUInstallDirs)
 include(CheckCXXCompilerFlag)
 include(cmake/FindCompilerFlag.cmake)

diff --git a/examples/cpp/CMakeLists.txt b/examples/cpp/CMakeLists.txt
@@ -2,6 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 
 include_directories(${CMAKE_SOURCE_DIR}/src/cc)
+include_directories(${CMAKE_SOURCE_DIR}/src/cc/api)
 
 option(INSTALL_CPP_EXAMPLES "Install C++ examples. Those binaries are statically linked and can take plenty of disk space" OFF)
 

diff --git a/src/cc/CMakeLists.txt b/src/cc/CMakeLists.txt
@@ -28,18 +28,17 @@ set(bcc_common_sources bpf_common.cc bpf_module.cc exported_files.cc)
 set(bcc_table_sources table_storage.cc shared_table.cc bpffs_table.cc json_map_decl_visitor.cc)
 set(bcc_util_sources ns_guard.cc common.cc)
 set(bcc_sym_sources bcc_syms.cc bcc_elf.c bcc_perf_map.c bcc_proc.c)
-set(bcc_api_sources BPF.cc BPFTable.cc)
 
 add_library(bcc-shared SHARED
+ link_all.cc
  ${bcc_common_sources} ${bcc_table_sources} ${bcc_sym_sources}
- ${bcc_util_sources} ${bcc_api_sources})
+ ${bcc_util_sources})
 set_target_properties(bcc-shared PROPERTIES VERSION ${REVISION_LAST} SOVERSION 0)
 set_target_properties(bcc-shared PROPERTIES OUTPUT_NAME bcc)
 
 add_library(bcc-loader-static STATIC ${bcc_sym_sources} ${bcc_util_sources})
 add_library(bcc-static STATIC
- ${bcc_common_sources} ${bcc_table_sources}
- ${bcc_util_sources} ${bcc_api_sources})
+ ${bcc_common_sources} ${bcc_table_sources} ${bcc_util_sources})
 set_target_properties(bcc-static PROPERTIES OUTPUT_NAME bcc)
 
 include(clang_libs)
@@ -50,6 +49,13 @@ set(bcc_common_libs b_frontend clang_frontend bpf-static
  ${clang_libs} ${llvm_libs} ${LIBELF_LIBRARIES})
 
 option(ENABLE_USDT "Enable User-level Statically Defined Tracing" ON)
+CMAKE_DEPENDENT_OPTION(ENABLE_CPP_API "Enable C++ API" ON "ENABLE_USDT" OFF)
+
+if(ENABLE_CPP_API)
+ add_subdirectory(api)
+ list(APPEND bcc_common_libs api-static)
+endif()
+
 if(ENABLE_USDT)
  add_subdirectory(usdt)
  list(APPEND bcc_common_libs usdt-static)
@@ -62,7 +68,7 @@ target_link_libraries(bcc-static ${bcc_common_libs} bcc-loader-static)
 install(TARGETS bcc-shared LIBRARY COMPONENT libbcc
  DESTINATION ${CMAKE_INSTALL_LIBDIR})
 install(FILES bpf_common.h bpf_module.h bcc_syms.h bcc_exception.h file_desc.h
- libbpf.h perf_reader.h BPF.h BPFTable.h
+ libbpf.h perf_reader.h
  table_desc.h table_storage.h COMPONENT libbcc
  DESTINATION include/bcc)
 install(DIRECTORY compat/linux/ COMPONENT libbcc

diff --git a/src/cc/BPF.cc → src/cc/api/BPF.cc b/src/cc/BPF.cc → src/cc/api/BPF.cc
diff --git a/src/cc/BPF.h → src/cc/api/BPF.h b/src/cc/BPF.h → src/cc/api/BPF.h
diff --git a/src/cc/BPFTable.cc → src/cc/api/BPFTable.cc b/src/cc/BPFTable.cc → src/cc/api/BPFTable.cc
diff --git a/src/cc/BPFTable.h → src/cc/api/BPFTable.h b/src/cc/BPFTable.h → src/cc/api/BPFTable.h
diff --git a/src/cc/api/CMakeLists.txt b/src/cc/api/CMakeLists.txt
@@ -0,0 +1,3 @@
+set(bcc_api_sources BPF.cc BPFTable.cc)
+add_library(api-static STATIC ${bcc_api_sources})
+install(FILES BPF.h BPFTable.h COMPONENT libbcc DESTINATION include/bcc)
diff --git a/src/cc/link_all.cc b/src/cc/link_all.cc
@@ -0,0 +1,21 @@
+// Copyright (c) 2017 VMware, Inc.
+// Licensed under the Apache License, Version 2.0 (the "License")
+#include <cstdlib>
+
+#include "bcc_usdt.h"
+
+namespace {
+ // Take this trick from llvm for forcing exported functions in helper
+ // libraries to be included in the final .so
+ struct LinkAll {
+ LinkAll() {
+ // getenv never returns -1, but compiler doesn't know!
+ if (::getenv("bar") != (char *)-1)
+ return;
+
+ (void)bcc_usdt_new_frompid(-1);
+ (void)bcc_usdt_new_frompath(nullptr);
+ (void)bcc_usdt_close(nullptr);
+ }
+ } LinkAll; // declare one instance to invoke the constructor
+}
diff --git a/tests/cc/CMakeLists.txt b/tests/cc/CMakeLists.txt
@@ -2,6 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 
 include_directories(${CMAKE_SOURCE_DIR}/src/cc)
+include_directories(${CMAKE_SOURCE_DIR}/src/cc/api)
 
 add_executable(test_static test_static.c)
 target_link_libraries(test_static bcc-static)