mirror of https://git.tukaani.org/xz.git
78 lines
3.2 KiB
Plaintext
78 lines
3.2 KiB
Plaintext
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# visibility.m4 serial 6
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dnl Copyright (C) 2005, 2008, 2010-2020 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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dnl From Bruno Haible.
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dnl Tests whether the compiler supports the command-line option
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dnl -fvisibility=hidden and the function and variable attributes
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dnl __attribute__((__visibility__("hidden"))) and
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dnl __attribute__((__visibility__("default"))).
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dnl Does *not* test for __visibility__("protected") - which has tricky
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dnl semantics (see the 'vismain' test in glibc) and does not exist e.g. on
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dnl Mac OS X.
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dnl Does *not* test for __visibility__("internal") - which has processor
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dnl dependent semantics.
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dnl Does *not* test for #pragma GCC visibility push(hidden) - which is
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dnl "really only recommended for legacy code".
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dnl Set the variable CFLAG_VISIBILITY.
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dnl Defines and sets the variable HAVE_VISIBILITY.
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AC_DEFUN([gl_VISIBILITY],
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[
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AC_REQUIRE([AC_PROG_CC])
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CFLAG_VISIBILITY=
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HAVE_VISIBILITY=0
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if test -n "$GCC"; then
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dnl First, check whether -Werror can be added to the command line, or
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dnl whether it leads to an error because of some other option that the
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dnl user has put into $CC $CFLAGS $CPPFLAGS.
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AC_CACHE_CHECK([whether the -Werror option is usable],
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[gl_cv_cc_vis_werror],
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[gl_save_CFLAGS="$CFLAGS"
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CFLAGS="$CFLAGS -Werror"
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AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM([[]], [[]])],
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[gl_cv_cc_vis_werror=yes],
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[gl_cv_cc_vis_werror=no])
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CFLAGS="$gl_save_CFLAGS"
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])
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dnl Now check whether visibility declarations are supported.
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AC_CACHE_CHECK([for simple visibility declarations],
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[gl_cv_cc_visibility],
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[gl_save_CFLAGS="$CFLAGS"
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CFLAGS="$CFLAGS -fvisibility=hidden"
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dnl We use the option -Werror and a function dummyfunc, because on some
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dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
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dnl "visibility attribute not supported in this configuration; ignored"
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dnl at the first function definition in every compilation unit, and we
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dnl don't want to use the option in this case.
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if test $gl_cv_cc_vis_werror = yes; then
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CFLAGS="$CFLAGS -Werror"
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fi
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AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
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extern __attribute__((__visibility__("default"))) int exportedvar;
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extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);
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extern __attribute__((__visibility__("default"))) int exportedfunc (void);
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void dummyfunc (void) {}
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]],
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[[]])],
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[gl_cv_cc_visibility=yes],
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[gl_cv_cc_visibility=no])
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CFLAGS="$gl_save_CFLAGS"
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])
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if test $gl_cv_cc_visibility = yes; then
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CFLAG_VISIBILITY="-fvisibility=hidden"
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HAVE_VISIBILITY=1
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fi
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fi
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AC_SUBST([CFLAG_VISIBILITY])
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AC_SUBST([HAVE_VISIBILITY])
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AC_DEFINE_UNQUOTED([HAVE_VISIBILITY], [$HAVE_VISIBILITY],
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[Define to 1 or 0, depending whether the compiler supports simple visibility declarations.])
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])
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