From e63470a43889be3f61c71ca31e57b4e3c3da5961 Mon Sep 17 00:00:00 2001
From: Ivan Trubach <mr.trubach@icloud.com>
Date: Sat, 17 Aug 2024 22:35:03 +0300
Subject: [PATCH 3/5] Do not search for a C++ compiler and set MAKE_CXX
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Removes unnecessary reference to C++ compiler if CXX is set to an
absolute path. If CXX is not an absolute path, we avoid defaulting CXX
to a compiler name that was used to build the package.

Context: GNU Make defines default values for CC, CXX and other
environment variables. For CXX, it usually defaults to g++, however,
FreeBSD and OpenBSD no longer ship GCC as a system compiler (and use
Clang instead). For C compiler, POSIX standardizes the name to be "cc",
but there is no such standard for C++ compiler name. As a fix, GNU Make
uses CXX set for build as a default (via MAKE_CXX preprocessor macro in
the source code).

We revert the change that added this behavior and set the default to c++
or g++ that does not depend on the build platform.

In stdenv, CXX environment variable is always defined and overrides the
default value.

References:
 • https://savannah.gnu.org/bugs/?63668
 • https://git.savannah.gnu.org/cgit/make.git/commit/?id=ffa28f3914ff402b3915f75e4fed86ac6fb1449d
---
 configure.ac  |  2 --
 src/default.c | 19 ++++++-------------
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/configure.ac b/configure.ac
index cd785754..41a65307 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,8 +37,6 @@ AM_INIT_AUTOMAKE([1.16.1 foreign -Werror -Wall])
 # Checks for programs.
 AC_USE_SYSTEM_EXTENSIONS
 AC_PROG_CC
-AC_PROG_CXX
-AC_DEFINE_UNQUOTED(MAKE_CXX, ["$CXX"], [Default C++ compiler.])
 
 # Configure gnulib
 gl_EARLY
diff --git a/src/default.c b/src/default.c
index e396269b..78ba402f 100644
--- a/src/default.c
+++ b/src/default.c
@@ -528,22 +528,15 @@ static const char *default_variables[] =
 #ifdef GCC_IS_NATIVE
     "CC", "gcc",
     "OBJC", "gcc",
+# ifdef __MSDOS__
+    "CXX", "gpp",       /* g++ is an invalid name on MSDOS */
+# else
+    "CXX", "g++",
+# endif /* __MSDOS__ */
 #else
     "CC", "cc",
     "OBJC", "cc",
-#endif
-#ifdef MAKE_CXX
-    "CXX", MAKE_CXX,
-#else
-# ifdef GCC_IS_NATIVE
-#  ifdef __MSDOS__
-    "CXX", "gpp",       /* g++ is an invalid name on MSDOS */
-#  else
-    "CXX", "gcc",
-#  endif /* __MSDOS__ */
-# else
-    "CXX", "g++",
-# endif
+    "CXX", "c++",
 #endif
     /* This expands to $(CO) $(COFLAGS) $< $@ if $@ does not exist,
        and to the empty string if $@ does exist.  */
-- 
2.51.2