1# visibility.m4 serial 4 (gettext-0.18.2) 2dnl Copyright (C) 2005, 2008, 2010-2011 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7dnl From Bruno Haible. 8 9dnl Tests whether the compiler supports the command-line option 10dnl -fvisibility=hidden and the function and variable attributes 11dnl __attribute__((__visibility__("hidden"))) and 12dnl __attribute__((__visibility__("default"))). 13dnl Does *not* test for __visibility__("protected") - which has tricky 14dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on 15dnl MacOS X. 16dnl Does *not* test for __visibility__("internal") - which has processor 17dnl dependent semantics. 18dnl Does *not* test for #pragma GCC visibility push(hidden) - which is 19dnl "really only recommended for legacy code". 20dnl Set the variable CFLAG_VISIBILITY. 21dnl Defines and sets the variable HAVE_VISIBILITY. 22 23AC_DEFUN([gl_VISIBILITY], 24[ 25 AC_REQUIRE([AC_PROG_CC]) 26 CFLAG_VISIBILITY= 27 HAVE_VISIBILITY=0 28 if test -n "$GCC"; then 29 dnl First, check whether -Werror can be added to the command line, or 30 dnl whether it leads to an error because of some other option that the 31 dnl user has put into $CC $CFLAGS $CPPFLAGS. 32 AC_MSG_CHECKING([whether the -Werror option is usable]) 33 AC_CACHE_VAL([gl_cv_cc_vis_werror], [ 34 gl_save_CFLAGS="$CFLAGS" 35 CFLAGS="$CFLAGS -Werror" 36 AC_COMPILE_IFELSE( 37 [AC_LANG_PROGRAM([[]], [[]])], 38 [gl_cv_cc_vis_werror=yes], 39 [gl_cv_cc_vis_werror=no]) 40 CFLAGS="$gl_save_CFLAGS"]) 41 AC_MSG_RESULT([$gl_cv_cc_vis_werror]) 42 dnl Now check whether visibility declarations are supported. 43 AC_MSG_CHECKING([for simple visibility declarations]) 44 AC_CACHE_VAL([gl_cv_cc_visibility], [ 45 gl_save_CFLAGS="$CFLAGS" 46 CFLAGS="$CFLAGS -fvisibility=hidden" 47 dnl We use the option -Werror and a function dummyfunc, because on some 48 dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning 49 dnl "visibility attribute not supported in this configuration; ignored" 50 dnl at the first function definition in every compilation unit, and we 51 dnl don't want to use the option in this case. 52 if test $gl_cv_cc_vis_werror = yes; then 53 CFLAGS="$CFLAGS -Werror" 54 fi 55 AC_COMPILE_IFELSE( 56 [AC_LANG_PROGRAM( 57 [[extern __attribute__((__visibility__("hidden"))) int hiddenvar; 58 extern __attribute__((__visibility__("default"))) int exportedvar; 59 extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void); 60 extern __attribute__((__visibility__("default"))) int exportedfunc (void); 61 void dummyfunc (void) {} 62 ]], 63 [[]])], 64 [gl_cv_cc_visibility=yes], 65 [gl_cv_cc_visibility=no]) 66 CFLAGS="$gl_save_CFLAGS"]) 67 AC_MSG_RESULT([$gl_cv_cc_visibility]) 68 if test $gl_cv_cc_visibility = yes; then 69 CFLAG_VISIBILITY="-fvisibility=hidden" 70 HAVE_VISIBILITY=1 71 fi 72 fi 73 AC_SUBST([CFLAG_VISIBILITY]) 74 AC_SUBST([HAVE_VISIBILITY]) 75 AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY], 76 [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.]) 77]) 78