Review comments.

Signed-off-by: fruffy <fruffy@nyu.edu>

CMakeLists.txt

@@ -43,7 +43,7 @@ OPTION (ENABLE_P4TC "Build the P4TC backend" ON)
 OPTION (ENABLE_P4FMT "Build the P4FMT backend" ON)
 OPTION (ENABLE_P4TEST "Build the P4Test backend (required for the full test suite)" ON)
 OPTION (ENABLE_TEST_TOOLS "Build the P4Tools development platform" OFF)
-OPTION (ENABLE_P4C_GRAPHS "Build the p4c-graphs backend" ON)
+OPTION (ENABLE_P4C_GRAPHS "Build the p4c-graphs backend" OFF)
 OPTION (ENABLE_PROTOBUF_STATIC "Link against Protobuf statically" ON)
 OPTION (ENABLE_GC "Compile with the Boehm-Demers-Weiser garbage collector." ON)
 OPTION (ENABLE_WERROR "Treat warnings as errors" OFF)
@@ -55,6 +55,7 @@ likely depend on the standard libary anyway. If you have some non-static C++ dep
 STATIC_BUILD_WITH_DYNAMIC_STDLIB." OFF)
 OPTION (STATIC_BUILD_WITH_DYNAMIC_STDLIB "Build a (mostly) statically linked release binary. \
 Glibc and C++ standard library is linked dynamically." OFF)
+set(ADDITIONAL_P4C_BOOST_LIBRARIES "" CACHE STRING "Build and make these additional boost modules available. Modules are separated with semicolons.")
 
 if (STATIC_BUILD_WITH_DYNAMIC_GLIBC OR STATIC_BUILD_WITH_DYNAMIC_STDLIB)
     # We want to optimize the binary size for a static release binary by default.
@@ -200,7 +201,10 @@ include(Abseil)
 p4c_obtain_abseil()
 include(Protobuf)
 p4c_obtain_protobuf()
-
+# The boost graph module is optional and only required by the graphs back end.
+if(ENABLE_P4C_GRAPHS AND NOT P4C_USE_PREINSTALLED_BOOST)
+  list(APPEND ADDITIONAL_P4C_BOOST_LIBRARIES graph)
+endif()
 include(Boost)
 p4c_obtain_boost()
 
@@ -456,7 +460,7 @@ endif ()
 if (ENABLE_EBPF)
     add_subdirectory (backends/ebpf)
 endif ()
-if (ENABLE_P4C_GRAPHS AND HAVE_LIBBOOST_GRAPH EQUAL 1)
+if (ENABLE_P4C_GRAPHS)
   add_subdirectory (backends/graphs)
 endif ()
 if (ENABLE_P4TC)

backends/graphs/CMakeLists.txt

@@ -12,6 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+if (P4C_USE_PREINSTALLED_BOOST)
+  find_package(Boost REQUIRED COMPONENTS graph)
+  set(HAVE_LIBBOOST_GRAPH 1)
+endif()
+
 configure_file("${CMAKE_CURRENT_SOURCE_DIR}/version.h.cmake"
   "${CMAKE_CURRENT_BINARY_DIR}/version.h" @ONLY)
 

backends/graphs/graphs.h

@@ -20,12 +20,6 @@ limitations under the License.
 #include "config.h"
 #include "lib/cstring.h"
 
-/// Shouldn't happen as cmake will not try to build this backend if the boost
-/// graph headers couldn't be found.
-#ifndef HAVE_LIBBOOST_GRAPH
-#error "This backend requires the boost graph headers, which could not be found"
-#endif
-
 #include <map>
 #include <optional>
 #include <utility>  // std::pair

cmake/Boost.cmake

@@ -13,20 +13,11 @@ macro(p4c_obtain_boost)
       set(Boost_USE_STATIC_LIBS ON)
       set(Boost_USE_STATIC_RUNTIME OFF)
     endif()
-
-    # The boost graph headers are optional and only required by the graphs back end.
-    find_package(Boost QUIET COMPONENTS graph)
-    if(Boost_FOUND)
-      set(HAVE_LIBBOOST_GRAPH 1)
-    else()
-      message(WARNING "Boost graph headers not found, will not build 'graphs' backend")
-    endif()
     find_package(Boost REQUIRED COMPONENTS iostreams)
     set(P4C_BOOST_LIBRARIES Boost::iostreams)
   else()
-    # This option can be used to include custom boost modules.
-    set(P4C_TARGET_BOOST_LIBRARIES "" CACHE STRING "Build and make these boost modules available. Modules are separated with semicolons.")
     set(P4C_BOOST_VERSION "1.86.0")
+    set(P4C_BOOST_HASH "2c5ec5edcdff47ff55e27ed9560b0a0b94b07bd07ed9928b476150e16b0efc57")
     message(STATUS "Fetching Boost version ${P4C_BOOST_VERSION} for P4C...")
     # Print out download state while setting up Boost.
     set(FETCHCONTENT_QUIET_PREV ${FETCHCONTENT_QUIET})
@@ -38,14 +29,9 @@ macro(p4c_obtain_boost)
     # Add boost modules.
     # format, multiprecision, and iostreams are needed by P4C core.
     set(BOOST_INCLUDE_LIBRARIES format multiprecision iostreams)
+    list(APPEND BOOST_INCLUDE_LIBRARIES ${ADDITIONAL_P4C_BOOST_LIBRARIES})
     set(BOOST_ENABLE_CMAKE ON)
 
-    # The boost graph module is optional and only required by the graphs back end.
-    if(ENABLE_P4C_GRAPHS)
-      set(HAVE_LIBBOOST_GRAPH 1)
-      list(APPEND BOOST_INCLUDE_LIBRARIES graph)
-    endif()
-    list(APPEND BOOST_INCLUDE_LIBRARIES ${P4C_TARGET_BOOST_LIBRARIES})
 
     # Always link local Boost statically.
     set(Boost_USE_STATIC_LIBS ON)
@@ -56,7 +42,7 @@ macro(p4c_obtain_boost)
     FetchContent_Declare(
         Boost
         URL https://github.com/boostorg/boost/releases/download/boost-${P4C_BOOST_VERSION}/boost-${P4C_BOOST_VERSION}-cmake.tar.xz
-        URL_HASH SHA256=2c5ec5edcdff47ff55e27ed9560b0a0b94b07bd07ed9928b476150e16b0efc57
+        URL_HASH SHA256=${P4C_BOOST_HASH}
         USES_TERMINAL_DOWNLOAD TRUE
         GIT_PROGRESS TRUE
     )