cpp: Set default visibility of all symbols to hidden

* configure.ac: Add -fvisibility=hidden to GPGME_CPP_CFLAGS if gcc
supports the flag.
* lang/cpp/src/Makefile.am (AM_CPPFLAGS): Add GPGME_CPP_CFLAGS.
* m4/ax_gcc_func_attribute.m4: New.
--

With this change all defined symbols are hidden by default, so that they
are not exported anymore. All symbols that are part of the ABI and that
shall still be exported are already marked as having default visibility.

The m4 macro was taken from the website mentioned in the License header
of the file.

GnuPG-bug-id: 5906
This commit is contained in:
Ingo Klöcker 2022-03-28 17:17:41 +02:00
parent 92139e7b6b
commit fe588fef09
3 changed files with 254 additions and 3 deletions

View File

@ -331,8 +331,6 @@ for language in $enabled_languages; do
fi
done
# Enable C++ 11 if cpp language is requested
LIST_MEMBER("cpp", $enabled_languages)
if test "$found" = "1"; then
@ -354,6 +352,16 @@ if test "$found" = "1"; then
fi
fi
# Check whether compiler supports visibility attribute (if cpp language is enabled)
LIST_MEMBER("cpp", $enabled_languages)
if test "$found" = "1"; then
AX_GCC_FUNC_ATTRIBUTE(visibility)
if test "$ax_cv_have_func_attribute_visibility" = "yes"; then
GPGME_CPP_CFLAGS="$GPGME_CPP_CFLAGS -fvisibility=hidden"
fi
fi
AC_SUBST(GPGME_CPP_CFLAGS)
# Check that if qt is enabled cpp also is enabled
LIST_MEMBER("qt", $enabled_languages)
if test "$found" = "1"; then

View File

@ -71,7 +71,8 @@ nodist_gpgmeppinclude_HEADERS = gpgmepp_version.h
libgpgmepp_la_SOURCES = $(main_sources) $(gpgmepp_headers) context_vanilla.cpp \
$(interface_headers) $(private_gpgmepp_headers)
AM_CPPFLAGS = -I$(top_builddir)/src @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
AM_CPPFLAGS = -I$(top_builddir)/src \
@GPGME_CPP_CFLAGS@ @GPG_ERROR_CFLAGS@ @LIBASSUAN_CFLAGS@ \
-DBUILDING_GPGMEPP -Wsuggest-override \
-Wzero-as-null-pointer-constant

242
m4/ax_gcc_func_attribute.m4 Normal file
View File

@ -0,0 +1,242 @@
# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_gcc_func_attribute.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_GCC_FUNC_ATTRIBUTE(ATTRIBUTE)
#
# DESCRIPTION
#
# This macro checks if the compiler supports one of GCC's function
# attributes; many other compilers also provide function attributes with
# the same syntax. Compiler warnings are used to detect supported
# attributes as unsupported ones are ignored by default so quieting
# warnings when using this macro will yield false positives.
#
# The ATTRIBUTE parameter holds the name of the attribute to be checked.
#
# If ATTRIBUTE is supported define HAVE_FUNC_ATTRIBUTE_<ATTRIBUTE>.
#
# The macro caches its result in the ax_cv_have_func_attribute_<attribute>
# variable.
#
# The macro currently supports the following function attributes:
#
# alias
# aligned
# alloc_size
# always_inline
# artificial
# cold
# const
# constructor
# constructor_priority for constructor attribute with priority
# deprecated
# destructor
# dllexport
# dllimport
# error
# externally_visible
# fallthrough
# flatten
# format
# format_arg
# gnu_format
# gnu_inline
# hot
# ifunc
# leaf
# malloc
# noclone
# noinline
# nonnull
# noreturn
# nothrow
# optimize
# pure
# sentinel
# sentinel_position
# unused
# used
# visibility
# warning
# warn_unused_result
# weak
# weakref
#
# Unsupported function attributes will be tested with a prototype
# returning an int and not accepting any arguments and the result of the
# check might be wrong or meaningless so use with care.
#
# LICENSE
#
# Copyright (c) 2013 Gabriele Svelto <gabriele.svelto@gmail.com>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 13
AC_DEFUN([AX_GCC_FUNC_ATTRIBUTE], [
AS_VAR_PUSHDEF([ac_var], [ax_cv_have_func_attribute_$1])
AC_CACHE_CHECK([for __attribute__(($1))], [ac_var], [
AC_LINK_IFELSE([AC_LANG_PROGRAM([
m4_case([$1],
[alias], [
int foo( void ) { return 0; }
int bar( void ) __attribute__(($1("foo")));
],
[aligned], [
int foo( void ) __attribute__(($1(32)));
],
[alloc_size], [
void *foo(int a) __attribute__(($1(1)));
],
[always_inline], [
inline __attribute__(($1)) int foo( void ) { return 0; }
],
[artificial], [
inline __attribute__(($1)) int foo( void ) { return 0; }
],
[cold], [
int foo( void ) __attribute__(($1));
],
[const], [
int foo( void ) __attribute__(($1));
],
[constructor_priority], [
int foo( void ) __attribute__((__constructor__(65535/2)));
],
[constructor], [
int foo( void ) __attribute__(($1));
],
[deprecated], [
int foo( void ) __attribute__(($1("")));
],
[destructor], [
int foo( void ) __attribute__(($1));
],
[dllexport], [
__attribute__(($1)) int foo( void ) { return 0; }
],
[dllimport], [
int foo( void ) __attribute__(($1));
],
[error], [
int foo( void ) __attribute__(($1("")));
],
[externally_visible], [
int foo( void ) __attribute__(($1));
],
[fallthrough], [
void foo( int x ) {switch (x) { case 1: __attribute__(($1)); case 2: break ; }};
],
[flatten], [
int foo( void ) __attribute__(($1));
],
[format], [
int foo(const char *p, ...) __attribute__(($1(printf, 1, 2)));
],
[gnu_format], [
int foo(const char *p, ...) __attribute__((format(gnu_printf, 1, 2)));
],
[format_arg], [
char *foo(const char *p) __attribute__(($1(1)));
],
[gnu_inline], [
inline __attribute__(($1)) int foo( void ) { return 0; }
],
[hot], [
int foo( void ) __attribute__(($1));
],
[ifunc], [
int my_foo( void ) { return 0; }
static int (*resolve_foo(void))(void) { return my_foo; }
int foo( void ) __attribute__(($1("resolve_foo")));
],
[leaf], [
__attribute__(($1)) int foo( void ) { return 0; }
],
[malloc], [
void *foo( void ) __attribute__(($1));
],
[noclone], [
int foo( void ) __attribute__(($1));
],
[noinline], [
__attribute__(($1)) int foo( void ) { return 0; }
],
[nonnull], [
int foo(char *p) __attribute__(($1(1)));
],
[noreturn], [
void foo( void ) __attribute__(($1));
],
[nothrow], [
int foo( void ) __attribute__(($1));
],
[optimize], [
__attribute__(($1(3))) int foo( void ) { return 0; }
],
[pure], [
int foo( void ) __attribute__(($1));
],
[sentinel], [
int foo(void *p, ...) __attribute__(($1));
],
[sentinel_position], [
int foo(void *p, ...) __attribute__(($1(1)));
],
[returns_nonnull], [
void *foo( void ) __attribute__(($1));
],
[unused], [
int foo( void ) __attribute__(($1));
],
[used], [
int foo( void ) __attribute__(($1));
],
[visibility], [
int foo_def( void ) __attribute__(($1("default")));
int foo_hid( void ) __attribute__(($1("hidden")));
int foo_int( void ) __attribute__(($1("internal")));
int foo_pro( void ) __attribute__(($1("protected")));
],
[warning], [
int foo( void ) __attribute__(($1("")));
],
[warn_unused_result], [
int foo( void ) __attribute__(($1));
],
[weak], [
int foo( void ) __attribute__(($1));
],
[weakref], [
static int foo( void ) { return 0; }
static int bar( void ) __attribute__(($1("foo")));
],
[
m4_warn([syntax], [Unsupported attribute $1, the test may fail])
int foo( void ) __attribute__(($1));
]
)], [])
],
dnl GCC doesn't exit with an error if an unknown attribute is
dnl provided but only outputs a warning, so accept the attribute
dnl only if no warning were issued.
[AS_IF([grep -- -Wattributes conftest.err],
[AS_VAR_SET([ac_var], [no])],
[AS_VAR_SET([ac_var], [yes])])],
[AS_VAR_SET([ac_var], [no])])
])
AS_IF([test yes = AS_VAR_GET([ac_var])],
[AC_DEFINE_UNQUOTED(AS_TR_CPP(HAVE_FUNC_ATTRIBUTE_$1), 1,
[Define to 1 if the system has the `$1' function attribute])], [])
AS_VAR_POPDEF([ac_var])
])