cmake/FindPCAP: fix use of bad cached function checks

When libpcap-dev is not installed, do not look for functions like
pcap_datalink_name_to_val since the negative result would be cached.
Then after installing libpcap-dev, the build would fail due to
redeclaration of functions.

Change-Id: Ifdbad09e9cf160383b16b6459693f7ea5d65b9c3
Reviewed-on: https://code.wireshark.org/review/18834
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 48 insertions, 46 deletions

diff --git a/cmake/modules/FindPCAP.cmake b/cmake/modules/FindPCAP.cmake
index c362cc0c3b..69dffba4a1 100644
--- a/cmake/modules/FindPCAP.cmake
+++ b/cmake/modules/FindPCAP.cmake
@@ -43,54 +43,56 @@ else()
   set( PCAP_LIBRARIES )
 endif()
 
-#Functions
-include( CMakePushCheckState )
-include( CheckFunctionExists )
-include( CheckVariableExists )
+if( PCAP_FOUND )
+  #Functions
+  include( CMakePushCheckState )
+  include( CheckFunctionExists )
+  include( CheckVariableExists )
 
-cmake_push_check_state()
-set( CMAKE_REQUIRED_INCLUDES ${PCAP_INCLUDE_DIRS} )
-set( CMAKE_REQUIRED_LIBRARIES ${PCAP_LIBRARIES} )
+  cmake_push_check_state()
+  set( CMAKE_REQUIRED_INCLUDES ${PCAP_INCLUDE_DIRS} )
+  set( CMAKE_REQUIRED_LIBRARIES ${PCAP_LIBRARIES} )
 
-check_function_exists( "pcap_open_dead" HAVE_PCAP_OPEN_DEAD )
-check_function_exists( "pcap_freecode" HAVE_PCAP_FREECODE )
-#
-# Note: for pcap_breakloop() and pcap_findalldevs(), the autoconf script
-# checks for more than just whether the function exists, it also checks
-# for whether pcap.h declares it; Mac OS X software/security updates can
-# update libpcap without updating the headers.
-#
-check_function_exists( "pcap_breakloop" HAVE_PCAP_BREAKLOOP )
-check_function_exists( "pcap_create" HAVE_PCAP_CREATE )
-if( HAVE_PCAP_CREATE OR WIN32 )
- #
- # If we have pcap_create(), we have pcap_set_buffer_size(), and
- # can set the capture buffer size.
- #
- # Otherwise, if this is Windows, we have pcap_setbuff(), and can
- # set the capture buffer size.
- #
- set( CAN_SET_CAPTURE_BUFFER_SIZE TRUE )
-endif()
-check_function_exists( "pcap_datalink_name_to_val" HAVE_PCAP_DATALINK_NAME_TO_VAL )
-check_function_exists( "pcap_datalink_val_to_description" HAVE_PCAP_DATALINK_VAL_TO_DESCRIPTION )
-check_function_exists( "pcap_datalink_val_to_name" HAVE_PCAP_DATALINK_VAL_TO_NAME )
-check_function_exists( "pcap_findalldevs" HAVE_PCAP_FINDALLDEVS )
-check_function_exists( "pcap_free_datalinks" HAVE_PCAP_FREE_DATALINKS )
-check_function_exists( "pcap_get_selectable_fd" HAVE_PCAP_GET_SELECTABLE_FD )
-check_function_exists( "pcap_lib_version" HAVE_PCAP_LIB_VERSION )
-check_function_exists( "pcap_list_datalinks" HAVE_PCAP_LIST_DATALINKS )
-check_function_exists( "pcap_set_datalink" HAVE_PCAP_SET_DATALINK )
-check_function_exists( "bpf_image" HAVE_BPF_IMAGE )
-check_function_exists( "pcap_setsampling" HAVE_PCAP_SETSAMPLING )
-check_function_exists( "pcap_set_tstamp_precision" HAVE_PCAP_SET_TSTAMP_PRECISION )
-# Remote pcap checks
-check_function_exists( "pcap_open" HAVE_PCAP_OPEN )
-if( HAVE_PCAP_OPEN )
-  set( HAVE_PCAP_REMOTE 1 )
-  set( HAVE_REMOTE 1 )
-endif()
+  check_function_exists( "pcap_open_dead" HAVE_PCAP_OPEN_DEAD )
+  check_function_exists( "pcap_freecode" HAVE_PCAP_FREECODE )
+  #
+  # Note: for pcap_breakloop() and pcap_findalldevs(), the autoconf script
+  # checks for more than just whether the function exists, it also checks
+  # for whether pcap.h declares it; Mac OS X software/security updates can
+  # update libpcap without updating the headers.
+  #
+  check_function_exists( "pcap_breakloop" HAVE_PCAP_BREAKLOOP )
+  check_function_exists( "pcap_create" HAVE_PCAP_CREATE )
+  if( HAVE_PCAP_CREATE OR WIN32 )
+    #
+    # If we have pcap_create(), we have pcap_set_buffer_size(), and
+    # can set the capture buffer size.
+    #
+    # Otherwise, if this is Windows, we have pcap_setbuff(), and can
+    # set the capture buffer size.
+    #
+    set( CAN_SET_CAPTURE_BUFFER_SIZE TRUE )
+  endif()
+  check_function_exists( "pcap_datalink_name_to_val" HAVE_PCAP_DATALINK_NAME_TO_VAL )
+  check_function_exists( "pcap_datalink_val_to_description" HAVE_PCAP_DATALINK_VAL_TO_DESCRIPTION )
+  check_function_exists( "pcap_datalink_val_to_name" HAVE_PCAP_DATALINK_VAL_TO_NAME )
+  check_function_exists( "pcap_findalldevs" HAVE_PCAP_FINDALLDEVS )
+  check_function_exists( "pcap_free_datalinks" HAVE_PCAP_FREE_DATALINKS )
+  check_function_exists( "pcap_get_selectable_fd" HAVE_PCAP_GET_SELECTABLE_FD )
+  check_function_exists( "pcap_lib_version" HAVE_PCAP_LIB_VERSION )
+  check_function_exists( "pcap_list_datalinks" HAVE_PCAP_LIST_DATALINKS )
+  check_function_exists( "pcap_set_datalink" HAVE_PCAP_SET_DATALINK )
+  check_function_exists( "bpf_image" HAVE_BPF_IMAGE )
+  check_function_exists( "pcap_setsampling" HAVE_PCAP_SETSAMPLING )
+  check_function_exists( "pcap_set_tstamp_precision" HAVE_PCAP_SET_TSTAMP_PRECISION )
+  # Remote pcap checks
+  check_function_exists( "pcap_open" HAVE_PCAP_OPEN )
+  if( HAVE_PCAP_OPEN )
+    set( HAVE_PCAP_REMOTE 1 )
+    set( HAVE_REMOTE 1 )
+  endif()
 
-cmake_pop_check_state()
+  cmake_pop_check_state()
+endif()
 
 mark_as_advanced( PCAP_LIBRARIES PCAP_INCLUDE_DIRS )