[Buildroot] [PATCH v2 1/3] package/collectd: enforce c++17

[Michael Nosthoff via buildroot <buildroot@buildroot.org>]

abseil since 20250512.0 and hence protobuf/grpc now need C++17.
collectd in the currently used version sets C++ to 11.
So bump the C++ Version used when building collectd like it was done
before to bump it to C++14 in commit 5fcc4e19602ad37d018ccf3543fe82a291837f43
with patch 0002.

Signed-off-by: Michael Nosthoff <buildroot@heine.tech>

--

V2: reworded to be more clear that it is not fixing a currently happening issue
---
 ...005-configure.ax-fix-grpc-build-2025.patch | 73 +++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 package/collectd/0005-configure.ax-fix-grpc-build-2025.patch

diff --git a/package/collectd/0005-configure.ax-fix-grpc-build-2025.patch b/package/collectd/0005-configure.ax-fix-grpc-build-2025.patch
new file mode 100644
index 0000000000..e750483135
--- /dev/null
+++ b/package/collectd/0005-configure.ax-fix-grpc-build-2025.patch
@@ -0,0 +1,73 @@
+From 42b2ede4dadcf88293e408bcdf5645995b61b148 Mon Sep 17 00:00:00 2001
+From: Michael Nosthoff <buildroot@heine.tech>
+Date: Wed, 29 Oct 2025 16:48:20 +0100
+Subject: [PATCH] configure.ac: fix grpc build
+
+Similar to the previous "configure.ac: fix grpc build" commit:
+Google bumped it's compiler requirements again [1], hence the c++ version needs to be adjusted to c++17 to be able to build with the latest grpc versions.
+
+[1] https://github.com/google/oss-policies-info/blob/a5e3ed43d45ad615a20201cea8f7282f595555da/foundational-cxx-support-matrix.md
+
+Signed-off-by: Michael Nosthoff <buildroot@heine.tech>
+Upstream: https://github.com/collectd/collectd/commit/42b2ede4dadcf88293e408bcdf5645995b61b148
+---
+ configure.ac | 16 ++++++++--------
+ 1 file changed, 8 insertions(+), 8 deletions(-)
+
+diff --git a/configure.ac b/configure.ac
+index 8aa03fce63..eb6cbbc5d5 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -2844,20 +2844,20 @@ PKG_CHECK_MODULES([GRPCPP], [grpc++],
+ fi
+ 
+ if test "x$withval" != "xno"; then
+-  AC_MSG_CHECKING([whether $CXX accepts -std=c++14])
+-  if test_cxx_flags -std=c++14; then
++  AC_MSG_CHECKING([whether $CXX accepts -std=c++17])
++  if test_cxx_flags -std=c++17; then
+     AC_MSG_RESULT([yes])
+   else
+     AC_MSG_RESULT([no])
+-    with_libgrpcpp="no (requires C++14 support)"
+-    with_libprotobuf="no (<absl/base/policy_checks.h> requires C++14 support)"
++    with_libgrpcpp="no (requires C++17 support)"
++    with_libprotobuf="no (<absl/base/policy_checks.h> requires C++17 support)"
+   fi
+ fi
+ 
+ if test "x$with_libgrpcpp" = "xyes"; then
+   AC_LANG_PUSH(C++)
+   SAVE_CPPFLAGS="$CPPFLAGS"
+-  CPPFLAGS="-std=c++14 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS $CPPFLAGS"
++  CPPFLAGS="-std=c++17 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS $CPPFLAGS"
+   AC_CHECK_HEADERS([grpc++/grpc++.h],
+     [with_libgrpcpp="yes"],
+     [with_libgrpcpp="no (<grpc++/grpc++.h> not found)"]
+@@ -2871,7 +2871,7 @@ if test "x$with_libgrpcpp" = "xyes"; then
+   SAVE_CPPFLAGS="$CPPFLAGS"
+   SAVE_LDFLAGS="$LDFLAGS"
+   SAVE_LIBS="$LIBS"
+-  CPPFLAGS="-std=c++14 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS $CPPFLAGS"
++  CPPFLAGS="-std=c++17 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS $CPPFLAGS"
+   LDFLAGS="$with_libgrpcpp_ldflags"
+   if test "x$GRPCPP_LIBS" = "x"; then
+     LIBS="-lgrpc++"
+@@ -2899,7 +2899,7 @@ if test "x$with_libgrpcpp" = "xyes"; then
+   AC_LANG_POP(C++)
+ fi
+ 
+-BUILD_WITH_LIBGRPCPP_CPPFLAGS="-std=c++14 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS"
++BUILD_WITH_LIBGRPCPP_CPPFLAGS="-std=c++17 $with_libgrpcpp_cppflags $GRPCPP_CFLAGS"
+ BUILD_WITH_LIBGRPCPP_LDFLAGS="$with_libgrpcpp_ldflags"
+ BUILD_WITH_LIBGRPCPP_LIBS="$GRPCPP_LIBS"
+ AC_SUBST([BUILD_WITH_LIBGRPCPP_CPPFLAGS])
+@@ -4843,7 +4843,7 @@ if test "x$withval" != "xno"; then
+   AC_CHECK_LIB([protobuf], [main],
+     [
+       SAVE_CPPFLAGS="$CPPFLAGS"
+-      CPPFLAGS="-std=c++14 $with_libprotobuf_cppflags $PROTOBUF_CFLAGS"
++      CPPFLAGS="-std=c++17 $with_libprotobuf_cppflags $PROTOBUF_CFLAGS"
+       if test "x$PROTOBUF_LIBS" = "x"
+       then
+         PROTOBUF_LIBS="-lprotobuf"
-- 
2.43.0

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