fix cmake issue with referencing a non-existing function argument (#1118)

according to https://cmake.org/cmake/help/latest/command/function.html, "Referencing to ARGV# arguments beyond ARGC have undefined behavior.", which I hit with cmake 3.19.7. This uses ARGC to check whether ARGV1 has been passed before referencing it.

fix cmake issue with referencing a non-existing function argument (#1118)
d882be1e · Kai Germaschewski · GitHub · 058fb588 · d882be1e
Unverified Commit d882be1e authored Apr 26, 2021 by Kai Germaschewski Committed by GitHub Apr 26, 2021
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Showing with 8 additions and 4 deletions

AddCXXCompilerFlag.cmake cmake/AddCXXCompilerFlag.cmake +8 -4

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--- a/cmake/AddCXXCompilerFlag.cmake
+++ b/cmake/AddCXXCompilerFlag.cmake
@@ -34,9 +34,11 @@ function(add_cxx_compiler_flag FLAG)
  check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
  set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
  if(${MANGLED_FLAG})
-    set(VARIANT ${ARGV1})
+    if(ARGC GREATER 1)
-    if(ARGV1)
+      set(VARIANT ${ARGV1})
      string(TOUPPER "_${VARIANT}" VARIANT)
+    else()
+      set(VARIANT "")
    endif()
    set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${BENCHMARK_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
  endif()
@@ -49,9 +51,11 @@ function(add_required_cxx_compiler_flag FLAG)
  check_cxx_compiler_flag("${FLAG}" ${MANGLED_FLAG})
  set(CMAKE_REQUIRED_FLAGS "${OLD_CMAKE_REQUIRED_FLAGS}")
  if(${MANGLED_FLAG})
-    set(VARIANT ${ARGV1})
+    if(ARGC GREATER 1)
-    if(ARGV1)
+      set(VARIANT ${ARGV1})
      string(TOUPPER "_${VARIANT}" VARIANT)
+    else()
+      set(VARIANT "")
    endif()
    set(CMAKE_CXX_FLAGS${VARIANT} "${CMAKE_CXX_FLAGS${VARIANT}} ${FLAG}" PARENT_SCOPE)
    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${FLAG}" PARENT_SCOPE)