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Diffstat (limited to '')
| -rw-r--r-- | m4/visibility.m4 | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/m4/visibility.m4 b/m4/visibility.m4 new file mode 100644 index 0000000..8c266a8 --- /dev/null +++ b/m4/visibility.m4 @@ -0,0 +1,77 @@ +# visibility.m4 serial 6 +dnl Copyright (C) 2005, 2008, 2010-2019 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) {} + ]], + [[]])], + [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.]) +]) |