build: Fix trailing semicolon check for GCC pedantic warnings

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

@@ -54,9 +54,25 @@ if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
         "GNU ${CMAKE_CXX_COMPILER_VERSION} ${below_minimum_msg} ${GNU_MinVersion}"
     )
   endif()
-  if((CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.0.0"))
-    set(GCC_PEDANTIC_SEMICOLON TRUE)
+
+  # Check if pedantic throws warning in trailing semicolon after {} scope
+  # (frequently used to make macros look like functions)
+  include(CheckCXXSourceCompiles)
+  set(CMAKE_REQUIRED_FLAGS "-Wall -Wpedantic -Werror")
+  check_cxx_source_compiles(
+    "
+      int test(){ return 0; };
+      int main(){
+        return test();
+      }
+  "
+    GCC_WORKING_PEDANTIC_SEMICOLON
+  )
+  unset(CMAKE_REQUIRED_FLAGS)
+  if("${GCC_WORKING_PEDANTIC_SEMICOLON}" STREQUAL "")
+    set(GCC_WORKING_PEDANTIC_SEMICOLON 0)
   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

@@ -221,9 +221,7 @@ macro(process_options)
       endif()
     else()
       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))
+      if(${GCC_WORKING_PEDANTIC_SEMICOLON})
         add_compile_options(-Wpedantic)
       endif()
       if(${NS3_WARNINGS_AS_ERRORS})