From 53835355b0e51fbea8b8338882e147f3133a8984 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Sun, 22 Jan 2023 09:44:50 -0500
Subject: [PATCH] Add CFG_CXXFLAGS_STD so CFG_CXXFLAGS_STD_NEWEST can still
 exist (#3881)

---
 configure.ac              | 16 +++++++++-------
 include/verilated.mk.in   |  6 ++++--
 test_regress/Makefile_obj |  2 +-
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/configure.ac b/configure.ac
index 4a7eaa9df..95234386e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -532,21 +532,22 @@ AC_DEFUN([_MY_CXX_CHECK_CXX_VER],
      [_my_result=no])
    ])
 
-# Add $CFG_CXXFLAGS_STD_NEWEST only if can't compile correctly otherwise,
+# Add $CFG_CXXFLAGS_STD only if can't compile correctly otherwise,
 # as adding std= when not needed can cause errors with the C++ std library.
+CFG_CXXFLAGS_STD=$CFG_CXXFLAGS_STD_NEWEST
 AC_MSG_CHECKING(whether $CXX supports C++11)
 _MY_CXX_CHECK_CXX_VER()
 AC_MSG_RESULT($_my_result)
 if test "$_my_result" = "no" ; then
-   CXXFLAGS="$CXXFLAGS $CFG_CXXFLAGS_STD_NEWEST"
-   CFG_CXX_FLAGS_CMAKE="$CFG_CXX_FLAGS_CMAKE $CFG_CXXFLAGS_STD_NEWEST"
-   AC_MSG_CHECKING(whether $CXX supports C++11 with $CFG_CXXFLAGS_STD_NEWEST)
+   CXXFLAGS="$CXXFLAGS $CFG_CXXFLAGS_STD"
+   CFG_CXX_FLAGS_CMAKE="$CFG_CXX_FLAGS_CMAKE $CFG_CXXFLAGS_STD"
+   AC_MSG_CHECKING(whether $CXX supports C++11 with $CFG_CXXFLAGS_STD)
    _MY_CXX_CHECK_CXX_VER()
    AC_MSG_RESULT($_my_result)
 else
-  # CFG_CXXFLAGS_STD_NEWEST is also propagated to include/verilated.mk.in
-  # make sure we use the same std flag while compiling verilator and verilated design
-  CFG_CXXFLAGS_STD_NEWEST=""
+   # CFG_CXXFLAGS_STD is also propagated to include/verilated.mk.in
+   # make sure we use the same std flag while compiling verilator and verilated design
+   CFG_CXXFLAGS_STD=""
 fi
 if test "$_my_result" = "no" ; then
    AC_MSG_NOTICE([[]])
@@ -555,6 +556,7 @@ if test "$_my_result" = "no" ; then
 Verilator requires a C++11 or newer compiler.]])
 
 fi
+AC_SUBST(CFG_CXXFLAGS_STD)
 
 # Checks for library functions.
 AC_CHECK_MEMBER([struct stat.st_mtim.tv_nsec],
diff --git a/include/verilated.mk.in b/include/verilated.mk.in
index 60d6f726f..8e040cd79 100644
--- a/include/verilated.mk.in
+++ b/include/verilated.mk.in
@@ -21,7 +21,9 @@ CFG_WITH_LONGTESTS = @CFG_WITH_LONGTESTS@
 
 # Compiler flags to enable profiling
 CFG_CXXFLAGS_PROFILE = @CFG_CXXFLAGS_PROFILE@
-# Select newest language
+# Select language required to compile (often empty)
+CFG_CXXFLAGS_STD = @CFG_CXXFLAGS_STD@
+# Select newest language (unused by this Makefile, for some test's Makefiles)
 CFG_CXXFLAGS_STD_NEWEST = @CFG_CXXFLAGS_STD_NEWEST@
 # Compiler flags to use to turn off unused and generated code warnings, such as -Wno-div-by-zero
 CFG_CXXFLAGS_NO_UNUSED = @CFG_CXXFLAGS_NO_UNUSED@
@@ -140,7 +142,7 @@ endif
 #######################################################################
 ##### Threaded builds
 
-CPPFLAGS += $(CFG_CXXFLAGS_STD_NEWEST)
+CPPFLAGS += $(CFG_CXXFLAGS_STD)
 LDLIBS += $(CFG_LDLIBS_THREADS)
 
 ifneq ($(VM_TIMING),0)
diff --git a/test_regress/Makefile_obj b/test_regress/Makefile_obj
index 82962f1b3..237ab1224 100644
--- a/test_regress/Makefile_obj
+++ b/test_regress/Makefile_obj
@@ -41,7 +41,7 @@ CPPFLAGS += $(CPPFLAGS_ADD)
 
 ifeq ($(CFG_WITH_LONGTESTS),yes)
   ifeq ($(DRIVER_STD),newest)
-    CPPFLAGS += $(CFG_CXXFLAGS_STD_NEWEST)
+    CPPFLAGS += $(CFG_CXXFLAGS_STD)
   endif
 endif