build: Disable pedantic checks in GCC9 due to extra semicolon check

build-support/custom-modules/ns3-compiler-and-linker-support.cmake

@@ -54,6 +54,9 @@ if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
         "GNU ${CMAKE_CXX_COMPILER_VERSION} ${below_minimum_msg} ${GNU_MinVersion}"
     )
   endif()
+  if((CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.0.0"))
+    set(GCC_PEDANTIC_SEMICOLON TRUE)
+  endif()
   if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "12.2.0"))
     # PCH causes weird errors on certain versions of GCC when C++20 is enabled
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106799

build-support/macros-and-definitions.cmake

@@ -220,7 +220,12 @@ macro(process_options)
         add_compile_options(/WX)
       endif()
     else()
-      add_compile_options(-Wall -Wpedantic) # -Wextra
+      add_compile_options(-Wall) # -Wextra
+      # Pedantic checks in GCC < 10 include extra semicolon, which we use a lot
+      # to make macros look like function calls
+      if(NOT (DEFINED GCC_PEDANTIC_SEMICOLON))
+        add_compile_options(-Wpedantic)
+      endif()
       if(${NS3_WARNINGS_AS_ERRORS})
         add_compile_options(-Werror -Wno-error=deprecated-declarations)
       endif()