Add compiletime-assert.h for COMPILETIME_ASSERT() macro

C11 has added static_assert(EXPR, MSG) to assert.h, but C99
only knows runtime assertions using assert(EXPR). This
defines the COMPILETIME_ASSERT(EXPR) macro which works with
both C11 and later using static_assert(), and another way
if compiling using a pre-C11 language standard.

2 files changed, 95 insertions, 0 deletions

diff --git a/libgphoto2_port/libgphoto2_port/Makefile.am b/libgphoto2_port/libgphoto2_port/Makefile.am
index dfbad73a9..0119253e0 100644
--- a/libgphoto2_port/libgphoto2_port/Makefile.am
+++ b/libgphoto2_port/libgphoto2_port/Makefile.am
@@ -6,6 +6,9 @@ EXTRA_DIST =
 EXTRA_DIST += i18n.h
 
 
+EXTRA_DIST += compiletime-assert.h
+
+
 lib_LTLIBRARIES                  = libgphoto2_port.la
 libgphoto2_port_la_CFLAGS        =
 libgphoto2_port_la_CPPFLAGS      =
diff --git a/libgphoto2_port/libgphoto2_port/compiletime-assert.h b/libgphoto2_port/libgphoto2_port/compiletime-assert.h
new file mode 100644
index 000000000..4c046e76e
--- /dev/null
+++ b/libgphoto2_port/libgphoto2_port/compiletime-assert.h
@@ -0,0 +1,92 @@
+/** \file libgphoto2_port/compiletime-assert.h
+ * \brief Allow compile time assertions with or without C11.
+ *
+ * C11 has added static_assert(EXPR, MSG) to assert.h, but C99 only
+ * knows runtime assertions using assert(EXPR). This defines
+ * COMPILETIME_ASSERT(EXPR) which works with both C99 and C11 and
+ * later.
+ *
+ * \author Copyright (C) 2010-2021 Hans Ulrich Niedermann <hun@n-dimensional.de>
+ *
+ * \copyright GNU Lesser General Public License 2 or later
+ *
+ * This library 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 of the License, or (at your option) any later version.
+ *
+ * This library 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301  USA
+ */
+
+#ifndef LIBGPHOTO2_PORT_COMPILETIME_ASSERT_H
+#define LIBGPHOTO2_PORT_COMPILETIME_ASSERT_H
+
+
+#if (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L))
+/* C11 or later */
+
+#include <assert.h>
+
+/** Compiletime assertion for use inside a function. */
+#define COMPILETIME_ASSERT(CONDITION) \
+	static_assert((CONDITION), #CONDITION)
+
+/** Compiletime assertion for use outside a function. */
+#define BARE_COMPILETIME_ASSERT(CONDITION) \
+	static_assert((CONDITION), #CONDITION)
+
+#else
+/* before C11 */
+
+/** Compiletime assertion for use inside a function. */
+#define COMPILETIME_ASSERT(CONDITION)				      \
+	switch (0) {      /* error here means assertion has failed */ \
+	case 0:           /* error here means assertion has failed */ \
+	case (CONDITION): /* error here means assertion has failed */ \
+		break;						      \
+	}
+
+
+/** \internal used by BARE_COMPILETIME_ASSERT() macro */
+#define MAKE_BARE_COMPILETIME_ASSERT_NAME				\
+	MAKE_BARE_COMPILETIME_ASSERT_NAME1(COMPILETIME_ASSERT_fails_in_line, \
+					   __LINE__)
+
+
+/** \internal used by BARE_COMPILETIME_ASSERT() macro */
+#define MAKE_BARE_COMPILETIME_ASSERT_NAME1(BASE, PARAM) \
+	MAKE_BARE_COMPILETIME_ASSERT_NAME2(BASE, PARAM)
+
+
+/** \internal used by BARE_COMPILETIME_ASSERT() macro */
+#define MAKE_BARE_COMPILETIME_ASSERT_NAME2(BASE, PARAM) \
+	BASE ## _ ## PARAM
+
+
+/** Compiletime assertion for use outside a function. */
+#define BARE_COMPILETIME_ASSERT(CONDITION)		\
+	void MAKE_BARE_COMPILETIME_ASSERT_NAME(void);	\
+	void MAKE_BARE_COMPILETIME_ASSERT_NAME(void)	\
+	{						\
+		COMPILETIME_ASSERT(CONDITION);		\
+	}
+
+#endif /* after/before C11 */
+
+
+#endif /* !defined(LIBGPHOTO2_PORT_COMPILETIME_ASSERT_H) */
+
+/*
+ * Local Variables:
+ * c-file-style:"linux"
+ * indent-tabs-mode:t
+ * End:
+ */