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List:       openvpn-devel
Subject:    [Openvpn-devel] [PATCH v2 1/2] Remove flexible array member autoconf check
From:       Arne Schwabe <arne () rfc2549 ! org>
Date:       2021-03-28 14:20:37
Message-ID: 20210328142038.8826-1-arne () rfc2549 ! org
[Download RAW message or body]

This is configure macro that tries out how to declare a variable array
at the end of struct. This has been standardised in C99, so there is
no more need for non C99 magic. See also this stackoverflow discussion:

https://stackoverflow.com/questions/14643406/whats-the-need-of-array-with-zero-elements

Patch V2: Also remove AX_EMPTY_ARRAY from configure.ac

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 config-msvc.h           |  1 -
 configure.ac            |  1 -
 m4/ax_emptyarray.m4     | 40 ----------------------------------------
 src/openvpn/circ_list.h |  2 +-
 src/openvpn/syshead.h   |  2 --
 5 files changed, 1 insertion(+), 45 deletions(-)
 delete mode 100644 m4/ax_emptyarray.m4

diff --git a/config-msvc.h b/config-msvc.h
index e430ca96f..0260927ce 100644
--- a/config-msvc.h
+++ b/config-msvc.h
@@ -119,7 +119,6 @@
 #define inline __inline
 #endif
 
-#define EMPTY_ARRAY_SIZE 0
 #define TARGET_WIN32 1
 #define TARGET_ALIAS "Windows-MSVC"
 
diff --git a/configure.ac b/configure.ac
index 428bebeda..c17266a0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -421,7 +421,6 @@ AC_TYPE_SIGNAL
 AX_CPP_VARARG_MACRO_ISO
 AX_CPP_VARARG_MACRO_GCC
 AX_TYPE_SOCKLEN_T
-AX_EMPTY_ARRAY
 AC_CHECK_SIZEOF([unsigned int])
 AC_CHECK_SIZEOF([unsigned long])
 AC_CHECK_HEADERS([ \
diff --git a/m4/ax_emptyarray.m4 b/m4/ax_emptyarray.m4
deleted file mode 100644
index c6781c179..000000000
--- a/m4/ax_emptyarray.m4
+++ /dev/null
@@ -1,40 +0,0 @@
-dnl @synopsis AX_EMPTY_ARRAY
-dnl
-dnl Define EMPTY_ARRAY_SIZE to be either "0"
-dnl or "" depending on which syntax the compiler
-dnl prefers for empty arrays in structs.
-dnl
-dnl @version
-dnl @author James Yonan <jim@yonan.net>
-AC_DEFUN([AX_EMPTY_ARRAY], [
-	AS_VAR_PUSHDEF([VAR],[ax_cv_c_empty_array])dnl
-	AC_CACHE_CHECK(
-		[for C compiler empty array size],
-		[VAR],
-		[AC_COMPILE_IFELSE(
-			[AC_LANG_PROGRAM(
-				,
-				[[
-struct { int foo; int bar[0]; } mystruct;
-				]]
-			)],
-			[VAR=0],
-			[AC_COMPILE_IFELSE(
-				[AC_LANG_PROGRAM(
-					,
-					[[
-struct { int foo; int bar[]; } mystruct;
-					]]
-				)],
-				[VAR=],
-				[AC_MSG_ERROR([C compiler is unable to creaty empty arrays])]
-			)]
-		)]
-	)dnl
-	AC_DEFINE_UNQUOTED(
-		[EMPTY_ARRAY_SIZE],
-		[$VAR],
-		[Dimension to use for empty array declaration]
-	)dnl
-	AS_VAR_POPDEF([VAR])dnl
-])
diff --git a/src/openvpn/circ_list.h b/src/openvpn/circ_list.h
index 23b42d2ab..ba9115eab 100644
--- a/src/openvpn/circ_list.h
+++ b/src/openvpn/circ_list.h
@@ -34,7 +34,7 @@
         int x_size; \
         int x_cap; \
         int x_sizeof; \
-        type x_list[EMPTY_ARRAY_SIZE]; \
+        type x_list[]; \
     }
 
 #define CIRC_LIST_PUSH(obj, item) \
diff --git a/src/openvpn/syshead.h b/src/openvpn/syshead.h
index 5ee9bf1e8..cf9714593 100644
--- a/src/openvpn/syshead.h
+++ b/src/openvpn/syshead.h
@@ -392,8 +392,6 @@ typedef int MIB_TCP_STATE;
 #ifdef PEDANTIC
 #undef HAVE_CPP_VARARG_MACRO_GCC
 #undef HAVE_CPP_VARARG_MACRO_ISO
-#undef EMPTY_ARRAY_SIZE
-#define EMPTY_ARRAY_SIZE 1
 #undef inline
 #define inline
 #endif
-- 
2.30.1



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