commit 53d8ff41a2809b91b3e5d35b1fe0fecfbacaeb70
parent f6c159604efa9a7c6a79dd682924c1fb3368f4c3
Author: Evgeny Grin (Karlson2k) <k2k@drgrin.dev>
Date: Wed, 27 Aug 2025 17:18:14 +0200
configure: check for constexpr support
Diffstat:
4 files changed, 116 insertions(+), 1 deletion(-)
diff --git a/configure.ac b/configure.ac
@@ -1383,6 +1383,56 @@ AS_IF([test "x$ac_cv_c_inline" != "xno" && test "x${mhd_cv_cc_kwd_forceinline}"
SAVE_ac_c_werror_flag="$ac_c_werror_flag"
ac_c_werror_flag="yes"
+AC_CACHE_CHECK([whether 'constexpr' keywords supported by $CC],[mhd_cv_cc_kwd_constexpr],
+ [
+ AC_LINK_IFELSE([
+ AC_LANG_SOURCE([[
+
+static constexpr int zero_const_expr_s = 0;
+constexpr unsigned int one_const_expr_u = 1;
+
+enum some_Enm
+{
+ enm_Val_Zero = 0,
+ enm_Val_One = one_const_expr_u,
+ enm_Val_Two = 2
+};
+
+int main(int argc, char *argv[])
+{
+ enum some_Enm local_e_var;
+ static constexpr unsigned int arr0[1 + zero_const_expr_s] = { one_const_expr_u };
+ constexpr int arr1[one_const_expr_u] = { zero_const_expr_s };
+
+ switch(argc)
+ {
+ case zero_const_expr_s:
+ local_e_var = enm_Val_One;
+ break;
+ case 1:
+ local_e_var = enm_Val_Zero;
+ break;
+ case 10:
+ local_e_var = enm_Val_Two;
+ break;
+ default:
+ local_e_var = enm_Val_Two;
+ break;
+ }
+
+ return (arr0[0] + (unsigned int)local_e_var) ==
+ one_const_expr_u ? (arr1[0] - zero_const_expr_s) : (!! argv[0]);
+}
+ ]]
+ )
+ ],
+ [mhd_cv_cc_kwd_constexpr="yes"],[mhd_cv_cc_kwd_constexpr="no"]
+ )
+ ]
+)
+AS_VAR_IF([mhd_cv_cc_kwd_constexpr],["yes"],
+ [AC_DEFINE([MHD_HAVE_C_CONSTEXPR],[1],[Define to '1' if compiler supports "constexpr" keyword])]
+)
AC_CACHE_CHECK([for 'unreachable' keywords supported by $CC],[mhd_cv_cc_kwd_unreachable],
[
mhd_cv_cc_kwd_unreachable="none"
diff --git a/src/incl_priv/mhd_sys_options.h b/src/incl_priv/mhd_sys_options.h
@@ -631,6 +631,7 @@
# define mhd_FALLTHROUGH ((void) 0)
# undef _Atomic
# define _Atomic /* empty */
+# undef MHD_HAVE_C_CONSTEXPR
#endif
/* Avoid interference with third-party headers */
diff --git a/src/mhd2/Makefile.am b/src/mhd2/Makefile.am
@@ -35,7 +35,7 @@ libmicrohttpd2_la_SOURCES = \
compat_calloc.h \
sys_w32_ver.h \
mhd_align.h mhd_bithelpers.h mhd_byteorder.h \
- mhd_assert.h mhd_unreachable.h \
+ mhd_constexpr.h mhd_assert.h mhd_unreachable.h \
mhd_cntnr_ptr.h mhd_arr_num_elems.h \
mhd_tristate.h mhd_status_code_int.h \
mhd_socket_type.h mhd_sockets_macros.h \
diff --git a/src/mhd2/mhd_constexpr.h b/src/mhd2/mhd_constexpr.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later OR (GPL-2.0-or-later WITH eCos-exception-2.0) */
+/*
+ This file is part of GNU libmicrohttpd.
+ Copyright (C) 2025 Evgeny Grin (Karlson2k)
+
+ GNU libmicrohttpd is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ GNU libmicrohttpd is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ Alternatively, you can redistribute GNU libmicrohttpd and/or
+ modify it under the terms of the GNU General Public License as
+ published by the Free Software Foundation; either version 2 of
+ the License, or (at your option) any later version, together
+ with the eCos exception, as follows:
+
+ As a special exception, if other files instantiate templates or
+ use macros or inline functions from this file, or you compile this
+ file and link it with other works to produce a work based on this
+ file, this file does not by itself cause the resulting work to be
+ covered by the GNU General Public License. However the source code
+ for this file must still be made available in accordance with
+ section (3) of the GNU General Public License v2.
+
+ This exception does not invalidate any other reasons why a work
+ based on this file might be covered by the GNU General Public
+ License.
+
+ You should have received copies of the GNU Lesser General Public
+ License and the GNU General Public License along with this library;
+ if not, see <https://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file src/mhd2/mhd_constexpr.h
+ * @brief The definition of the mhd_constexpr helper macro
+ * @author Karlson2k (Evgeny Grin)
+ */
+
+#ifndef MHD_CONSTEXPR_H
+#define MHD_CONSTEXPR_H 1
+
+#include "mhd_sys_options.h"
+
+#ifdef MHD_HAVE_C_CONSTEXPR
+/**
+ * Static compile-time constant.
+ * When used inside a function, must be placed before any code statements.
+ */
+# define mhd_constexpr static constexpr
+#else
+/**
+ * Static compile-time constant.
+ * When used inside a function, must be placed before any code statements.
+ */
+# define mhd_constexpr static const
+#endif
+
+#endif /* ! MHD_CONSTEXPR_H */
