Add support for the clang compiler; update RAII_VAR to use BlocksRuntime

RAII_VAR, which is used extensively in Asterisk to manage reference counted
resources, uses a GCC extension to automatically invoke a cleanup function
when a variable loses scope. While this functionality is incredibly useful
and has prevented a large number of memory leaks, it also prevents Asterisk
from being compiled with clang.

This patch updates the RAII_VAR macro such that it can be compiled with clang.
It makes use of the BlocksRuntime, which allows for a closure to be created
that performs the actual cleanup.

Note that this does not attempt to address the numerous warnings that the clang
compiler catches in Asterisk.

Much thanks for this patch goes to:
* The folks on StackOverflow who asked this question and Leushenko for
  providing the answer that formed the basis of this code:
  http://stackoverflow.com/questions/24959440/rewrite-gcc-cleanup-macro-with-nested-function-for-clang
* Diederik de Groot, who has been extremely patient in working on getting this
  patch into Asterisk.

Review: https://reviewboard.asterisk.org/r/4370/

ASTERISK-24133
ASTERISK-23666
ASTERISK-20399
ASTERISK-20850 #close
Reported by: Diederik de Groot
patches:
  RAII_CLANG.patch uploaded by Diederik de Groot (License 6600)
........

Merged revisions 432807 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@432808 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 53 insertions, 8 deletions

diff --git a/configure b/configure
index 3a681b564..c7c0608c9 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.ac Revision: 431092 .
+# From configure.ac Revision: 432281 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.69 for asterisk trunk.
 #
@@ -687,6 +687,8 @@ PBX_RTLD_NOLOAD
 PBX_GLOB_BRACE
 PBX_GLOB_NOMAGIC
 AST_RPATH
+AST_CLANG_BLOCKS
+AST_CLANG_BLOCKS_LIBS
 AST_NESTED_FUNCTIONS
 AST_NATIVE_ARCH
 AST_SHADOW_WARNINGS
@@ -17305,7 +17307,7 @@ fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for -Wtrampolines support" >&5
 $as_echo_n "checking for -Wtrampolines support... " >&6; }
-if $(${CC} -Wtrampolines -S -o /dev/null -xc /dev/null > /dev/null 2>&1); then
+if $(${CC} -Wtrampolines -Werror -S -o /dev/null -xc /dev/null > /dev/null 2>&1); then
 	{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
 	AST_TRAMPOLINES=-Wtrampolines
@@ -17374,14 +17376,32 @@ $as_echo "no" >&6; }
 fi
 
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fnested-functions" >&5
-$as_echo_n "checking for -fnested-functions... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
 main ()
 {
+
+		#if defined(__clang__)
+		choke
+		#endif
+
+  ;
+  return 0;
+}
+
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+				{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for gcc -fnested-functions" >&5
+$as_echo_n "checking for gcc -fnested-functions... " >&6; }
+		cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
 auto void foo(void); void foo(void) {}
   ;
   return 0;
@@ -17390,16 +17410,41 @@ _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-	AST_NESTED_FUNCTIONS=
+			AST_NESTED_FUNCTIONS=
 else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: required" >&5
-$as_echo "required" >&6; }
-	AST_NESTED_FUNCTIONS=-fnested-functions
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+			AST_NESTED_FUNCTIONS=-fnested-functions
 
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
 
+else
+
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for clang -fblocks" >&5
+$as_echo_n "checking for clang -fblocks... " >&6; }
+		if test "`echo "int main(){return ^{return 42;}();}" | ${CC} -o /dev/null -fblocks -x c - 2>&1`" = ""; then
+			AST_CLANG_BLOCKS_LIBS=""
+			AST_CLANG_BLOCKS="-Wno-unknown-warning-option -fblocks"
+			{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+		elif test "`echo "int main(){return ^{return 42;}();}" | ${CC} -o /dev/null -fblocks -x c -lBlocksRuntime - 2>&1`" = ""; then
+			AST_CLANG_BLOCKS_LIBS="-lBlocksRuntime"
+			AST_CLANG_BLOCKS="-fblocks"
+			{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+		else
+			as_fn_error $? "\"BlocksRuntime is required for clang\"" "$LINENO" 5
+		fi
+
+
+
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
 # Check whether --enable-rpath was given.
 if test "${enable_rpath+set}" = set; then :
   enableval=$enable_rpath; case "${enableval}" in