binutils-gdb/gnulib/import/m4/visibility.m4
Simon Marchi 5df4cba632 gdb: update gnulib import
This is mostly to get this commit from gnulib:

    e22cd2677a4b7beacbf30b93bb0559f7b89f96ce
    Add ‘extern "C"’ to count-one-bits.h etc.

... which fixes this compilation problem I observed with clang++:

      CXXLD  gdb
    arch/arm-get-next-pcs.o:arm-get-next-pcs.c:function thumb_get_next_pcs_raw(arm_get_next_pcs*): error: undefined reference to 'count_one_bits(unsigned int)'
    <more such undefined references>

I built-tested on GNU/Linux x86-64 (gcc-9 and clang-9) as well as with the
x86_64-w64-mingw32-gcc cross-compiler.

gnulib/ChangeLog:

	* update-gnulib.sh (GNULIB_COMMIT_SHA1): Bump to
	e22cd2677a4b7beacbf30b93bb0559f7b89f96ce.
	* Makefile.in, config.in, configure, import/*: Re-generate.
2020-02-22 20:37:18 -05:00

78 lines
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# visibility.m4 serial 6
dnl Copyright (C) 2005, 2008, 2010-2020 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.])
])