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

7 files changed, 127 insertions, 27 deletions

diff --git a/Makefile b/Makefile
index 66a8411eb..c2e1fba78 100644
--- a/Makefile
+++ b/Makefile
@@ -184,7 +184,7 @@ ifeq ($(findstring -Wall,$(_ASTCFLAGS) $(ASTCFLAGS)),)
   _ASTCFLAGS+=-Wall
 endif
 
-_ASTCFLAGS+=-Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations $(AST_NESTED_FUNCTIONS) $(DEBUG)
+_ASTCFLAGS+=-Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations $(AST_NESTED_FUNCTIONS) $(AST_CLANG_BLOCKS) $(DEBUG)
 ADDL_TARGETS=
 
 ifeq ($(AST_DEVMODE),yes)
@@ -931,7 +931,7 @@ nmenuselect: menuselect/nmenuselect menuselect-tree menuselect.makeopts
 	-@menuselect/nmenuselect menuselect.makeopts && (echo "menuselect changes saved!"; rm -f channels/h323/Makefile.ast main/asterisk) || echo "menuselect changes NOT saved!"
 
 # options for make in menuselect/
-MAKE_MENUSELECT=CC="$(BUILD_CC)" CXX="" LD="" AR="" RANLIB="" \
+MAKE_MENUSELECT=CC="$(CC)" CXX="$(CXX)" LD="" AR="" RANLIB="" \
 		CFLAGS="$(BUILD_CFLAGS)" LDFLAGS="$(BUILD_LDFLAGS)" \
 		$(MAKE) -C menuselect CONFIGURE_SILENT="--silent"
 
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
diff --git a/configure.ac b/configure.ac
index de90e6a32..edb4322b1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1078,7 +1078,7 @@ fi
 AC_SUBST(AST_DECLARATION_AFTER_STATEMENT)
 
 AC_MSG_CHECKING(for -Wtrampolines support)
-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
 	AC_MSG_RESULT(yes)
 	AST_TRAMPOLINES=-Wtrampolines
 else
@@ -1133,16 +1133,41 @@ fi
 AC_SUBST(AST_NATIVE_ARCH)
 
 dnl Nested functions required for RAII implementation
-AC_MSG_CHECKING(for -fnested-functions)
-AC_COMPILE_IFELSE(
-	dnl Prototype needed due to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36774
-	[AC_LANG_PROGRAM([], [auto void foo(void); void foo(void) {}])],
-	AC_MSG_RESULT(no)
-	[AST_NESTED_FUNCTIONS=],
-	AC_MSG_RESULT(required)
-	[AST_NESTED_FUNCTIONS=-fnested-functions]
+AC_LINK_IFELSE(
+	[AC_LANG_PROGRAM([], [
+		#if defined(__clang__)
+		choke
+		#endif
+		])
+	],[
+		dnl Nested functions required for RAII implementation
+		AC_MSG_CHECKING(for gcc -fnested-functions)
+		AC_COMPILE_IFELSE(
+			dnl Prototype needed due to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36774
+			[AC_LANG_PROGRAM([], [auto void foo(void); void foo(void) {}])],
+			AC_MSG_RESULT(no)
+			[AST_NESTED_FUNCTIONS=],
+			AC_MSG_RESULT(yes)
+			[AST_NESTED_FUNCTIONS=-fnested-functions]
+		)
+		AC_SUBST(AST_NESTED_FUNCTIONS)
+	],[
+		AC_MSG_CHECKING(for clang -fblocks)
+		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"]
+			AC_MSG_RESULT(yes)
+		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"]
+			AC_MSG_RESULT(yes)
+		else
+			AC_MSG_ERROR("BlocksRuntime is required for clang")
+		fi
+		AC_SUBST(AST_CLANG_BLOCKS_LIBS)
+		AC_SUBST(AST_CLANG_BLOCKS)
+	]
 )
-AC_SUBST(AST_NESTED_FUNCTIONS)
 
 dnl Check to see if rpath should be set in LDFLAGS
 AC_ARG_ENABLE(rpath,
diff --git a/include/asterisk/inline_api.h b/include/asterisk/inline_api.h
index 5f6911d36..d76dfa0a5 100644
--- a/include/asterisk/inline_api.h
+++ b/include/asterisk/inline_api.h
@@ -25,12 +25,14 @@
   Small API functions that are candidates for inlining need to be specially
   declared and defined, to ensure that the 'right thing' always happens.
   For example:
-  	- there must _always_ be a non-inlined version of the function
+	- there must _always_ be a non-inlined version of the function
 	available for modules compiled out of the tree to link to
 	- references to a function that cannot be inlined (for any
 	reason that the compiler deems proper) must devolve into an
 	'extern' reference, instead of 'static', so that multiple
-	copies of the function body are not built in different modules
+	copies of the function body are not built in different modules.
+	However, since this doesn't work for clang, we go with 'static'
+	anyway and hope for the best!
 	- when LOW_MEMORY is defined, inlining should be disabled
 	completely, even if the compiler is configured to support it
 
@@ -46,8 +48,12 @@
 #if !defined(LOW_MEMORY) && !defined(DISABLE_INLINE)
 
 #if !defined(AST_API_MODULE)
+#if defined(__clang__)
+#define AST_INLINE_API(hdr, body) static hdr; static inline hdr body
+#else /* if defined(__clang__) */
 #define AST_INLINE_API(hdr, body) hdr; extern inline hdr body
-#else
+#endif
+#else /* if !defined(AST_API_MODULE) */
 #define AST_INLINE_API(hdr, body) hdr; hdr body
 #endif
 
diff --git a/include/asterisk/utils.h b/include/asterisk/utils.h
index a0e7cb6bf..1dc351d0a 100644
--- a/include/asterisk/utils.h
+++ b/include/asterisk/utils.h
@@ -1005,12 +1005,33 @@ char *ast_utils_which(const char *binary, char *fullpath, size_t fullpath_size);
  * }
  * \endcode
  */
-#define RAII_VAR(vartype, varname, initval, dtor) \
-    /* Prototype needed due to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36774 */ \
-    auto void _dtor_ ## varname (vartype * v); \
-    void _dtor_ ## varname (vartype * v) { dtor(*v); } \
+
+#if defined(__clang__)
+
+#if defined(__has_feature) && __has_feature(blocks)
+typedef void (^_raii_cleanup_block_t)(void);
+static inline void _raii_cleanup_block(_raii_cleanup_block_t *b) { (*b)(); }
+
+#define RAII_VAR(vartype, varname, initval, dtor)                                                                \
+    _raii_cleanup_block_t _raii_cleanup_ ## varname __attribute__((cleanup(_raii_cleanup_block),unused)) = NULL; \
+    vartype varname = initval;                                                                                   \
+    _raii_cleanup_ ## varname = ^{ dtor(varname); }
+
+#else
+	#error "CLANG must support the 'blocks' feature to compile Asterisk."
+#endif /* #if defined(__has_feature) && __has_feature(blocks) */
+
+#elif defined(__GNUC__)
+
+#define RAII_VAR(vartype, varname, initval, dtor)                              \
+    auto void _dtor_ ## varname (vartype * v);                                 \
+    void _dtor_ ## varname (vartype * v) { dtor(*v); }                         \
     vartype varname __attribute__((cleanup(_dtor_ ## varname))) = (initval)
 
+#else
+    #error "Cannot compile Asterisk: unknown and unsupported compiler."
+#endif /* #if __GNUC__ */
+
 /*!
  * \brief Asterisk wrapper around crypt(3).
  *
diff --git a/main/Makefile b/main/Makefile
index 0fa219297..0a63c01a0 100644
--- a/main/Makefile
+++ b/main/Makefile
@@ -40,6 +40,7 @@ AST_LIBS+=$(JANSSON_LIB)
 AST_LIBS+=$(URIPARSER_LIB)
 AST_LIBS+=$(UUID_LIB)
 AST_LIBS+=$(CRYPT_LIB)
+AST_LIBS+=$(AST_CLANG_BLOCKS_LIBS)
 
 ifneq ($(findstring $(OSARCH), linux-gnu uclinux linux-uclibc kfreebsd-gnu),)
   ifneq ($(findstring LOADABLE_MODULES,$(MENUSELECT_CFLAGS)),)
diff --git a/makeopts.in b/makeopts.in
index a0faaee46..96b031bdd 100644
--- a/makeopts.in
+++ b/makeopts.in
@@ -109,6 +109,8 @@ AST_TRAMPOLINES=@AST_TRAMPOLINES@
 AST_NO_STRICT_OVERFLOW=@AST_NO_STRICT_OVERFLOW@
 AST_SHADOW_WARNINGS=@AST_SHADOW_WARNINGS@
 AST_NESTED_FUNCTIONS=@AST_NESTED_FUNCTIONS@
+AST_CLANG_BLOCKS=@AST_CLANG_BLOCKS@
+AST_CLANG_BLOCKS_LIBS=@AST_CLANG_BLOCKS_LIBS@
 AST_RPATH=@AST_RPATH@
 AST_FORTIFY_SOURCE=@AST_FORTIFY_SOURCE@
 AST_MARCH_NATIVE=@AST_MARCH_NATIVE@