Commit 6c3c9435 authored by Nick Mathewson's avatar Nick Mathewson 🤹
Browse files

Add a fallthrough macro. 

This macro defers to __attribute__((fallthrough)) on GCC (and
clang).  Previously we had been using GCC's magic /* fallthrough */
comments, but clang very sensibly doesn't accept those.

Since not all compiler recognize it, we only define it when our
configure script detects that it works.

Part of a fix for 34078.
parent d380acae

configure.ac

+16 −0
Original line number Diff line number Diff line
@@ -356,6 +356,22 @@ if test "$tor_cv_c_c99_designated_init" != "yes"; then 
  AC_MSG_ERROR([Your compiler doesn't support c99 designated initializers. This is required as of Tor 0.2.6.x])

fi



saved_CFLAGS="$CFLAGS"

CFLAGS="$CFLAGS -Werror"

AC_CACHE_CHECK([for __attribute__((fallthrough))],

      tor_cv_c_attr_fallthrough,

      [AC_COMPILE_IFELSE(

         [AC_LANG_PROGRAM([extern int x; void fn(void) ;],

	       [[ switch (x) { case 1: fn(); __attribute__((fallthrough));

                               case 2: fn(); break; } ]])],

	 [tor_cv_c_attr_fallthrough=yes],

	 [tor_cv_c_attr_fallthrough=no] )])

CFLAGS="$saved_CFLAGS"



if test "$tor_cv_c_attr_fallthrough" == "yes"; then

  AC_DEFINE(HAVE_ATTR_FALLTHROUGH, [1], [defined if we have the fallthrough attribute.])

fi



TORUSER=_tor

AC_ARG_WITH(tor-user,

        AS_HELP_STRING(--with-tor-user=NAME, [specify username for tor daemon]),

src/lib/cc/compat_compiler.h

+6 −0
Original line number Diff line number Diff line
@@ -50,6 +50,12 @@ 
#define CHECK_SCANF(formatIdx, firstArg)

#endif /* defined(__GNUC__) */



#if defined(HAVE_ATTR_FALLTHROUGH)

#define FALLTHROUGH __attribute__((fallthrough))

#else

#define FALLTHROUGH

#endif



/* What GCC do we have? */

#ifdef __GNUC__

#define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)