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| @@ -0,0 +1,78 @@ | ||
| # visibility.m4 serial 7 | ||
| dnl Copyright (C) 2005, 2008, 2010-2021 Free Software Foundation, Inc. | ||
| dnl This file is free software; the Free Software Foundation | ||
| dnl gives unlimited permission to copy and/or distribute it, | ||
| dnl with or without modifications, as long as this notice is preserved. | ||
|
|
||
| dnl From Bruno Haible. | ||
|
|
||
| dnl Tests whether the compiler supports the command-line option | ||
| dnl -fvisibility=hidden and the function and variable attributes | ||
| dnl __attribute__((__visibility__("hidden"))) and | ||
| dnl __attribute__((__visibility__("default"))). | ||
| dnl Does *not* test for __visibility__("protected") - which has tricky | ||
| dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on | ||
| dnl Mac OS X. | ||
| dnl Does *not* test for __visibility__("internal") - which has processor | ||
| dnl dependent semantics. | ||
| dnl Does *not* test for #pragma GCC visibility push(hidden) - which is | ||
| dnl "really only recommended for legacy code". | ||
| dnl Set the variable CFLAG_VISIBILITY. | ||
| dnl Defines and sets the variable HAVE_VISIBILITY. | ||
|
|
||
| AC_DEFUN([gl_VISIBILITY], | ||
| [ | ||
| AC_REQUIRE([AC_PROG_CC]) | ||
| CFLAG_VISIBILITY= | ||
| HAVE_VISIBILITY=0 | ||
| if test -n "$GCC"; then | ||
| dnl First, check whether -Werror can be added to the command line, or | ||
| dnl whether it leads to an error because of some other option that the | ||
| dnl user has put into $CC $CFLAGS $CPPFLAGS. | ||
| AC_CACHE_CHECK([whether the -Werror option is usable], | ||
| [gl_cv_cc_vis_werror], | ||
| [gl_save_CFLAGS="$CFLAGS" | ||
| CFLAGS="$CFLAGS -Werror" | ||
| AC_COMPILE_IFELSE( | ||
| [AC_LANG_PROGRAM([[]], [[]])], | ||
| [gl_cv_cc_vis_werror=yes], | ||
| [gl_cv_cc_vis_werror=no]) | ||
| CFLAGS="$gl_save_CFLAGS" | ||
| ]) | ||
| dnl Now check whether visibility declarations are supported. | ||
| AC_CACHE_CHECK([for simple visibility declarations], | ||
| [gl_cv_cc_visibility], | ||
| [gl_save_CFLAGS="$CFLAGS" | ||
| CFLAGS="$CFLAGS -fvisibility=hidden" | ||
| dnl We use the option -Werror and a function dummyfunc, because on some | ||
| dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning | ||
| dnl "visibility attribute not supported in this configuration; ignored" | ||
| dnl at the first function definition in every compilation unit, and we | ||
| dnl don't want to use the option in this case. | ||
| if test $gl_cv_cc_vis_werror = yes; then | ||
| CFLAGS="$CFLAGS -Werror" | ||
| fi | ||
| AC_COMPILE_IFELSE( | ||
| [AC_LANG_PROGRAM( | ||
| [[extern __attribute__((__visibility__("hidden"))) int hiddenvar; | ||
| extern __attribute__((__visibility__("default"))) int exportedvar; | ||
| extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void); | ||
| extern __attribute__((__visibility__("default"))) int exportedfunc (void); | ||
| void dummyfunc (void); | ||
| void dummyfunc (void) {} | ||
| ]], | ||
| [[]])], | ||
| [gl_cv_cc_visibility=yes], | ||
| [gl_cv_cc_visibility=no]) | ||
| CFLAGS="$gl_save_CFLAGS" | ||
| ]) | ||
| if test $gl_cv_cc_visibility = yes; then | ||
| CFLAG_VISIBILITY="-fvisibility=hidden" | ||
| HAVE_VISIBILITY=1 | ||
| fi | ||
| fi | ||
| AC_SUBST([CFLAG_VISIBILITY]) | ||
| AC_SUBST([HAVE_VISIBILITY]) | ||
| AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY], | ||
| [Define to 1 or 0, depending whether the compiler supports simple visibility declarations.]) | ||
| ]) |
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